Is this possible? I went into a Sprint store and they told me that it was against store policy to do that.
I really like this phone but I hate Cingular service it has to be the worst possible out there.
I appreciate any and all answers.
thanks in advance!
I beleive they are two different types.. Cingular is GSM .. I forget what sprint is.. but it's not GSM
nope wont work att is gsm sprint is cdma
so I guess I need to go back to cingular to still use this phone? Any others carriers I can use it on that may be worth my time?
Sprint uses CDMA, which is an old, OLD OOOOLLLLDDDD technology.
Sprint invested a lot in building the CDMA network in North America so they seem reluctant to abandon it, even if it is an inferior network infrastructure in nearly every measurable way.
With almost all other carriers, it is possible to unlock phones, swap SIM cards, etc., to change providers. With Sprint, it's not possible.
You could move to T-Mobile service easily. I'm not sure about Verizon.
Doom Tints said:
Sprint uses CDMA, which is an old, OLD OOOOLLLLDDDD technology.
Sprint invested a lot in building the CDMA network in North America so they seem reluctant to abandon it, even if it is an inferior network infrastructure in nearly every measurable way.
With almost all other carriers, it is possible to unlock phones, swap SIM cards, etc., to change providers. With Sprint, it's not possible.
You could move to T-Mobile service easily. I'm not sure about Verizon.
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Click to collapse
Very true. T-Mobile and AT&T are the only major GSM carriers in the USA. Verizon, like Sprint is CDMA.
American Networks
Cingular/AT&T = GSM
T-Mobile = GSM
Sprint+nextel = CDMA/TDMA
Verizon = CDMA
US Cellular = CDMA
Thats all I know, i will keep digging
Here's a list of current and future GSM carriers in the USA, most of which I've never heard of:
http://www.gsmworld.com/roaming/gsminfo/cou_us.shtml
So another big-ish player who uses GSM would be Alltel.
Here's a list of CDMA carriers, if interested:
http://www.rentcell.com/cdma-info.htm
um... alltel is most deff CDMA and dobson cellular systems (which at&t just bought) also uses GSM..
revol wireless is cdma
northcoast pcs is cdma also
No, this website is correct about Alltel. If you look at its GSM coverage map, their GSM coverage is a bit limited. It's just not GSM where you are.
I don't know about the others you mentioned, or care.
so do alltel phones run dual then? cdma/gsm? cuz ive NEVER seen a gsm alltel phone at the store.. unless that area you mentioned has special phones
dbroncos38 said:
Is this possible? I went into a Sprint store and they told me that it was against store policy to do that.
I really like this phone but I hate Cingular service it has to be the worst possible out there.
I appreciate any and all answers.
thanks in advance!
Click to expand...
Click to collapse
BEST POST EVER!
hahahahahahahahaha
Altell mainly uses CDMA in the US and only uses GSM for roaming partner revenue. CDMA is not old oudated technology either ATT/Cingular is using WCDMA now which is slightly different.
Sprint does have an equivalent to the 8525. It was the MDA and now it's the prophet I think - you may want to double check that. You should be able to ebay your 8525 for about as much as an ebay prophet will cost you.
hi
The prophet is also a GSM phone
as much as everyone hates at&t, i've had them for 10 years. Lately, the customer service has been much better, and I have never had a problem with service in my area. I would look over at my girlfriend's phone, which is T-Mobile, and then look over at my 8525, and when I had full service with at&t, she either had none or barely one bar. at&t is apparently spending $18 MIL a day putting up 70 new towers a week to expand not only the regular network, but the 3g network. also, if you go with t-mobile (correct me if i am wrong) but you won't get umts/hspda. good luck with your choice.
-Nstefanelli-
gthing said:
Sprint does have an equivalent to the 8525. It was the MDA and now it's the prophet I think - you may want to double check that. You should be able to ebay your 8525 for about as much as an ebay prophet will cost you.
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Click to collapse
Sprint has the PPC6800 and, VZW is rumored to soon have the XV6800. Both are the same phones that are labeled for each carrier. It is the HTC Mogul (TyTN with WM6 and slightly smaller).
As for which network strategy is better, that has become quite a religious war because there is not much different anymore. CDMA always had the technical advantage, but now with WCDMA, there is much more parity.
As for which one is older, GSM was there before CDMA. To me, the key benefit to GSM based networks is that they can be used almost anywhere (given the right radio frequencies in the phone). CDMA is limited.
Doom Tints said:
No, this website is correct about Alltel. If you look at its GSM coverage map, their GSM coverage is a bit limited. It's just not GSM where you are.
I don't know about the others you mentioned, or care.
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Click to collapse
Yes it is true that Alltel "owns" GSM, but that is because in 2005 they purchased a company called Western Wireless. They still run as two seperate companies. Alltel runs their network based completely on CDMA and has roaming agreements with Sprint and Verizon.
Here is a map for you: http://www.mountainwireless.com/Alltel_ww.jpg
Deadem said:
Altell mainly uses CDMA in the US and only uses GSM for roaming partner revenue. CDMA is not old oudated technology either ATT/Cingular is using WCDMA now which is slightly different.
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Click to collapse
ATT only have CDMA back then..then they upgraded their network to GSM and phase out the CDMA network to better compete with Cingular and T-mobile. Now with the merger between ATT and Cingular, they only have GSM networks. The new WCDMA is planned to boost its 3G speed.
It boils down to this: GSM is the worldwide standard for cellular phone communication, except in the U.S. If you never plan on travelling outside the U.S. then the CDMA technology is fine for you (Sprint, Verizon). If you ever think you may want to travel ANYWHERE outside the U.S. and take your phone with you for quick and easy communication, and maybe even data link, then consider GSM. In the U.S. that would be ATT/Cingular, T-Mobile (there may be a few new smaller outfits as well). ATT/Cingular leads the pack in 3G/HSDPA (cellular broadband) coverage.
Service seems to depend on who, at the present time, is #1 in subscribers and who is trying to BECOME #1. I originally had Verizon until my travels took me overseas frequently. Verizon's customer svc had started to fall off as far as I was concerned. My experience with ATT/Cingular's cust svc gets them a rating of 'Fair'--nothing spectacular, but I don't use cust svc very often and their signals are the best around.
Related
I have an Evo and I really want the tunderbolt. If I can somehow "put" it on sprint can I still use 3g? Do they use the same bands is what I'm asking.
Yes, they do. I used to have a fully functioning Sprint touch pro operating on Verizons network. But good luck getting either carrier to activate the others phones. I know Verizon closed that loophole years ago.
kdj67f said:
Yes, they do. I used to have a fully functioning Sprint touch pro operating on Verizons network. But good luck getting either carrier to activate the others phones. I know Verizon closed that loophole years ago.
Click to expand...
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ESN transplant
Halabeaster54 said:
I have an Evo and I really want the tunderbolt. If I can somehow "put" it on sprint can I still use 3g? Do they use the same bands is what I'm asking.
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Click to collapse
As it was said, the MEID / ESN could theoretically (and illegally lol) be modified to emulate a separate device. The phones themselves have very similar hardware in the fact that they can operate on either network. The 3G chipset includes two bands -
the 800MHz 'Cellular Band' which is preferred by Verizon, and
the 1900MHz 'PCS Band' which is preferred by Sprint.
It operates as a standard switching band unit, as it will operate in hybrids between bands and protocols (2G/3G) as it scans for networks.
To fully adapt a device to a different network environment, extensive and thorough programming is required, along with good relationships with people on the 'inside,' or people who can get a foreign device activated on the new network. Another option would simply be to pay for a Verizon plan, but operate the phone itself on the Sprint network by flashing a divested PRL, which tells the phone to primarily use Sprint's backhaul, or network, to carry a Verizon customer's traffic - or even vice versa.
Unfortunately, though, the 4G experience will not longer be. The 4G bands on the devices differ at the hardware level, so there is no possibility of transferring the device for use with foreign 4G networks.
Do you think hd2 owners who have at&t will get to use tmobiles wavelength and finally get more than edge network from this happening??
For reference if new to this subject at&t and tmobile both have an EDGE network on the same wavelength so on an unlocked tmobile hd2 one can use the slow 2g internet connection of at&t, but the 3g networks run off of different bands so an at&t # can't connect to any 3g whatsoever, with at&t's purchase of tmobile wouldn't at&t have to utilize tmobiles 3g wavelength in order to still provide 3g and 3.5g to everyone with tmobile phones that aren't compatible with at&t's current network? If so then I'm personally benefitting from this and finally getting a decent mobile data speed on my tmobile phone with my at&t network
Please don't bash at&t here, I know they suck, I've used their service for quite some time now, I'm just looking for opinions and facts on this matter
and I know euro hd2's already pick up at&t 3g, I'm talking about tmous hardware
From what I have read it seems that in a year or so if this deal is accepted by the FCC at&t will reuse and refit tmobiles network towers/equipment to use there 4g LTE network and give it a boost while removing T-Mobile service altogether causing us T-Mobile 3g/4g users to get new phones that work on AT&T's data network so in your case I highly doubt it there really isn't a benefit for AT&T or T-mobile other then T-Mobile users will be able to have different range of phones (mostly iPhone) I really hope the FCC denies this deal not only does it kills another service provider option limiting us to 3 major companies and forces people escaping the high price of service from sprint, Verizon, and At&t (I've been on them all and left because of price and QOS) but also makes AT&T top dog just because they bought out another company
Yea I read about this yesterday. Highly pissed off. I can't stand at&t. Crappy phone signal, high prices, and crappy customer service. I hope this deal does not go through. Just like when sprint was supposed to buy tmobile. Hopefully it's just a rumor.
XsceneXhippieX said:
Do you think hd2 owners who have at&t will get to use tmobiles wavelength and finally get more than edge network from this happening??
For reference if new to this subject at&t and tmobile both have an EDGE network on the same wavelength so on an unlocked tmobile hd2 one can use the slow 2g internet connection of at&t, but the 3g networks run off of different bands so an at&t # can't connect to any 3g whatsoever, with at&t's purchase of tmobile wouldn't at&t have to utilize tmobiles 3g wavelength in order to still provide 3g and 3.5g to everyone with tmobile phones that aren't compatible with at&t's current network? If so then I'm personally benefitting from this and finally getting a decent mobile data speed on my tmobile phone with my at&t network
Please don't bash at&t here, I know they suck, I've used their service for quite some time now, I'm just looking for opinions and facts on this matter
and I know euro hd2's already pick up at&t 3g, I'm talking about tmous hardware
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Click to collapse
Actually I have read that its the exact opposite......AT&T has planned to upgrade all of Tmobiles service towers to the 4G LTE, leaving all T-Mobile Branded 3g phones unable to access
robstillholdin said:
Actually I have read that its the exact opposite......AT&T has planned to upgrade all of Tmobiles service towers to the 4G LTE, leaving all T-Mobile Branded 3g phones unable to access
Click to expand...
Click to collapse
yeah, about 5 minutes after i posted this i saw the article stating that at&t is decommissioning tmobile's 3/3.5g towers to use them for their LTE, too bad at&t is already selling "4g" phones (ie the atrix and the inspire 4g) with no capability of utilizing TRUE 4g via LTE later on... anyone else think at&t will re-release said phones as LTE devices for $50 more than the hspa versions? i cant wait to switch to verizon personally, but im waiting for a htc pyramid compatible with verizons 4g network to switch
I received a letter from tmobile if I wanted to attend a meeting/conference for San Jose, Ca becuase my current phone service will be upgraded.... not removed....
Is this confirmed yet? If so, I am going to be HIGHLY pissed off. I HATE AT&T with a passion and refuse to use their service.
Is it possible to unlock my HD2 and my fiancee's Galaxy S Vibrant to use on Sprint or Verizon?
Specialk47150 said:
Is this confirmed yet? If so, I am going to be HIGHLY pissed off. I HATE AT&T with a passion and refuse to use their service.
Is it possible to unlock my HD2 and my fiancee's Galaxy S Vibrant to use on Sprint or Verizon?
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Click to collapse
No, only for gsm networks, which is now going through an approval process to become a single gsm network, not confirmed until the fcc gives the word though so keep your fingers crossed!
Sent from cyanogen mod 7
Specialk47150 said:
Is this confirmed yet? If so, I am going to be HIGHLY pissed off. I HATE AT&T with a passion and refuse to use their service.
Is it possible to unlock my HD2 and my fiancee's Galaxy S Vibrant to use on Sprint or Verizon?
Click to expand...
Click to collapse
No Tmobile and AT&T use sim cards and use totally different frequencies
If the deal passes I highly doubt that the T-mobile name will continue for long. Especially since both carriers operate on the voicestream network. This will combine T-mobile's few towers with ATT's many towers. But as someone mentioned earlier niether of these two have real 4G. It ticks me off when I see comercials calling it 4G. Only verizon is rolling out true 4G in LTE.
And in case you haven't heard. T-mobile was going down hill. They were losing money. There were talks of Sprint buying them at first. So it may be a good thing with ATT buying them up.
$39 Billion is a lot of scooby snacks... and though I am aware that there are several regulatory hurdles to clear (SEC and FCC at the moment), I assume these beeeeches will lawyer up and find a way.
So from what I understand (which admittedly is very little) the existing Tmob towers will be re-purposed for rolling out Ma Bell's LTE coverage (within 12 months). As we all know, Ma Bell and Tmob use different broadcast frequencies for their Mobile broadband. So essentially, within a years time... those whom own a Vibrant, Vib + or any other 3g enabled Tmob smartphone... will have a very expensive edge capable device... ewwwwwwww, really !?!?!?!?!?!
Has there been any other word on this... as in compensation, grandfathering of packages (AT&T data plans blow money-wise) etc...
I know we have some Tmob sources on this board... any whispers???
Vibrant supports GayT&T bands, im unlocked.
Sent from my SGH-T959 using XDA App
tng222 said:
Vibrant supports GayT&T bands, im unlocked.
Sent from my SGH-T959 using XDA App
Click to expand...
Click to collapse
Umts and hsupa ????
droppin the know...
Vibrant is supports some AT&T's 3G bands. Most of the time, you'll be on AT&T's 3G, but you can also get kicked down to edge if the area you're in doesn't support Vibrant's 3G bands.
Nope, it does 850mhz and 1900mhz, all bands. However, I will admit the phone has issues switching between GSM and WCDMA, so I set it to WCDMA only.
Sent from my SGH-T959 using XDA App
Read today that AT&T may have to divest part of T-Mobile to Sprint
http://www.tmonews.com/2011/03/analysts-say-att-will-have-to-divest-part-of-t-mobile-possibly-to-sprint/
T-Mobile is becoming a rag doll...
This is going to be more fun than the Sprint Nextel fiasco.
I don't think there is much mystery as to what will happen. This is AT&T we are talking about, after all.
While a nice bonus, the additional subscribers to AT&T's user base is really a secondary concern. AT&T's prime target were the (leases for) T-mobile's frequencies.
AT&T's network is already overloaded (thanks in part to weak infineon radio chipsets). They need to start the roll out to LTE to compete (verizon is already ahead of them), and they know that customers will cry foul and leave if their LTE and HSPA+ phones do not get service any faster than current 3G phones (see: Motorola Atrix).
So, what will happen to T-mobile users? Simple... AT&T will honor existing contracts and arrangements *for 2G/3G service* (T-mob does not have 4G, despite the marketing), and they will issue T-mobile users new phones (some discounted, I am sure) for use on AT&T's existing network.
What does this mean for T-mobile customers? Say good-bye to being able to answer a phone call at a concert or college football game. Being on the largest network means having to share bandwith/frequency with the largest number of users. They will fight for service with all those people with sh*tty iphone antennae.
Slower data, locked down Android phones, and higher rates for service if you want to sign a new agreement are what will inevitably happen. Current AT&T customers probably won't notice a difference unless they get an LTE phone (in which case they will get the faster data and non-overloaded service that T-mobile customers are used to).
T-mo 3G coverage will get better in smaller towns & cities, but this isn't much of an advantage for me since I live in a large city.
I hope that if that happens and I can't use my phone in their network, I'm given the option of just cancel my contract...
tng222 said:
Nope, it does 850mhz and 1900mhz, all bands. However, I will admit the phone has issues switching between GSM and WCDMA, so I set it to WCDMA only.
Sent from my SGH-T959 using XDA App
Click to expand...
Click to collapse
Really don't think so. FCC documents only say 1900MHz for 3G. Who knows though?
I just hope we can continue to use smartphones on prepaid plans. That's really why I left Ma Bell.
Tarzanman said:
I don't think there is much mystery as to what will happen. This is AT&T we are talking about, after all.
While a nice bonus, the additional subscribers to AT&T's user base is really a secondary concern. AT&T's prime target were the (leases for) T-mobile's frequencies.
AT&T's network is already overloaded (thanks in part to weak infineon radio chipsets). They need to start the roll out to LTE to compete (verizon is already ahead of them), and they know that customers will cry foul and leave if their LTE and HSPA+ phones do not get service any faster than current 3G phones (see: Motorola Atrix).
So, what will happen to T-mobile users? Simple... AT&T will honor existing contracts and arrangements *for 2G/3G service* (T-mob does not have 4G, despite the marketing), and they will issue T-mobile users new phones (some discounted, I am sure) for use on AT&T's existing network.
What does this mean for T-mobile customers? Say good-bye to being able to answer a phone call at a concert or college football game. Being on the largest network means having to share bandwith/frequency with the largest number of users. They will fight for service with all those people with sh*tty iphone antennae.
Slower data, locked down Android phones, and higher rates for service if you want to sign a new agreement are what will inevitably happen. Current AT&T customers probably won't notice a difference unless they get an LTE phone (in which case they will get the faster data and non-overloaded service that T-mobile customers are used to).
T-mo 3G coverage will get better in smaller towns & cities, but this isn't much of an advantage for me since I live in a large city.
Click to expand...
Click to collapse
i think t-mobile does a great job in coverage, i get full service in my neighborhood but i dont get 3g service, maybe this will help? if not i just want to cancel my contract and switch to verizon
After the merger is done and the network has switched over...Worse case, I hope to unlock, pop in a AT&T SIM continue to use my Vibrant mostly like nothing has changed. I don't know what effect flashing a Captivate modem would have. I'm not worried...yet.
I think AT&T might make a transitional phase (2-4yrs) for T-mobile existing customers(no new AWS phones) before switching all T-mobile network to AT&T frequencies.
http://www.cnet.com/8301-17918_1-20048020-85.html?tag=TOCmoreStories.0
I hope sprint gets it! I never had and never will have at&t.... I price checked with at&t a few days ago.. 210 dollars for 2 unlimited lines!?!? Data capped at 2Gigs.. And 10 bucks for every gig used after!? I pay 140 for two fully loaded vibrants. . Fack at&t
Sent from my SGH-T959 using XDA Premium App
nate420 said:
210 dollars for 2 unlimited lines!?!? Data capped at 2Gigs.. And 10 bucks for every gig used after!?
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Click to collapse
Unlimited...
gamikzone said:
i think t-mobile does a great job in coverage, i get full service in my neighborhood but i dont get 3g service, maybe this will help? if not i just want to cancel my contract and switch to verizon
Click to expand...
Click to collapse
Same Here. I have been with T-mobile for 7 years now and even though I moved from a "4G" area to an area where I only get Edge, i still have stayed with T-Mob, but I am hoping we get the option to cancel our contracts because that Thunderbolt from Verizon is looking good. My co-worker has one and let me mess with it and it is nice.
Tarzanman said:
I don't think there is much mystery as to what will happen. This is AT&T we are talking about, after all.
While a nice bonus, the additional subscribers to AT&T's user base is really a secondary concern. AT&T's prime target were the (leases for) T-mobile's frequencies.
AT&T's network is already overloaded (thanks in part to weak infineon radio chipsets). They need to start the roll out to LTE to compete (verizon is already ahead of them), and they know that customers will cry foul and leave if their LTE and HSPA+ phones do not get service any faster than current 3G phones (see: Motorola Atrix).
So, what will happen to T-mobile users? Simple... AT&T will honor existing contracts and arrangements *for 2G/3G service* (T-mob does not have 4G, despite the marketing), and they will issue T-mobile users new phones (some discounted, I am sure) for use on AT&T's existing network.
What does this mean for T-mobile customers? Say good-bye to being able to answer a phone call at a concert or college football game. Being on the largest network means having to share bandwith/frequency with the largest number of users. They will fight for service with all those people with sh*tty iphone antennae.
Slower data, locked down Android phones, and higher rates for service if you want to sign a new agreement are what will inevitably happen. Current AT&T customers probably won't notice a difference unless they get an LTE phone (in which case they will get the faster data and non-overloaded service that T-mobile customers are used to).
T-mo 3G coverage will get better in smaller towns & cities, but this isn't much of an advantage for me since I live in a large city.
Click to expand...
Click to collapse
T-Mobile has a better "4G" than AT&T does. Their HSPA+ is faster than AT&T's.
dligon said:
http://www.cnet.com/8301-17918_1-20048020-85.html?tag=TOCmoreStories.0
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Completely agree with the article.
They are allowing AT&T to be a monopoly again,after all the work it took to destroy the monopoly.The FCC should shot down this deal period.
Howdy kids,
Quick question for those with more knowhow/info on the LTE bands and carriers. In your opinion at this stage of the game... Which US S4 version will have the most compatibily domestically (formost) and internationally? I know he carries all get thier own hardware/modem... im just currious which phone i should try if i might end up switching carries after 6months or so (no contract).
thanks for your thoughts
If I had to guess, probably T-Mobile. Unfortunately where I live, T-Mobile is almost all 2G/3G so I have to go with Sprint CDMA. But GSM networks are definitely the most flexible if you travel.
Sarcron said:
If I had to guess, probably T-Mobile. Unfortunately where I live, T-Mobile is almost all 2G/3G so I have to go with Sprint CDMA. But GSM networks are definitely the most flexible if you travel.
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Click to collapse
If I had to guess I'd say AT&T...def not T-Mobile - although both are gsm which adds flexibility, T-Mobile has terrible service and AT&T has better service (not saying ATT has the best...but its def better than T-Mobile) and sprint service is pretty bad too...
Also keep in mind it depends on where you live. The above is based on where I love which is southern California (orange county)
But definitely go for either the T-Mobile or att as gsm networks seem to be the most flexible
Sent from my HTC PH39100 using Tapatalk 2
Yep, GSM all the way if you travel and probably the snapdragon for the LTE if you have it in your home area or roam frequently where it is available. I'd likely go AT&T for the coverage unless you are in an area where you get good Tmo service and seldom leave it. No reason not to save the ching and get a cheaper plan with Tmo in that case.
I'd also add that if you plan on going off-contract and paying the full phone price, T-Mobile has the advantage of offering much better prepaid plans with unlimited data.
At&t id say. The verizon one will to but im betting the bootloader will be locked up. Once a dev cracks it then im sure roms will follow.
I have a phone that I bought from Verizon and I have kept the unlimited data. I know all about my phone but next to nothing about my service.
My question is specifically about phablets (for example, this) which is basically a big ass phone, or a tablet with cell service, however you want to word it. I'd use it exclusively with bluetooth instead of holding the thing up to my head, don't worry.
I travel internationally and see them A LOT in other countries (they cannot help me though since I need one to use in the US). I am under the impression that VZ will not activate anything I did not buy from them. I don't know how solid this is but every VZ employee I have asked has confirmed this so far. I know in the past that it used to be as simple as switching out the SIM card but doubt this is still the case.
I'm sure there are some hardware specs (frequencies?) that I need to look at that would determine the LTE/4G/3G whatever compatibility, but I don't know the terminology. Also I'm not exactly sure what I'm looking at when it comes to CDMA vs GSM, only that blokes in England use GSM. Can you help me out?
Also, I am hesitant to leave VZ because of the unlimited data and the service coverage. I live in mildly populated CT, USA and would welcome a prepaid plan if data/service is comparable but don't even know where to begin looking.
Thank you in advance - I really don't have anyone else to ask about this stuff.
I'll try to make it simple for you. There are really two types of cell networks (not counting LTE, since all carriers are using that now here in the US): GSM and CDMA.
CDMA is what Verizon, Sprint, US Cellular, MetroPCS, Cricket, and maybe other smaller carriers use. It is based on a serial number called a ESN on older phones or MEID on newer phones (since the late 2000s). That serial number is burned into the programming of the phone on the ROM and cannot be changed very easily and is illegal to do so supposedly. There are two types of CDMA technology in use today, 1xRTT and EVDO (older analog was phased out a few years ago). 1xRTT or 1x as it's abbreviated, is a "2G" technology that allows for packet switched voice and SMS traffic, as well as very very slow data speeds (think 56k dialup). EVDO is strictly for data (the voice part was never added because they didn't want to pony up the cost of it) and is used in Rev 0 and Rev A EVDO. Most Verizon/Sprint 3G is Rev. A EVDO. It hits a max of 3.1Mbps down and if you get a call or text message, it drops to 1x and the 3g is suspended, unless you have a radio that can do both at once (HTC Thunderbolt). You activate by serial number and a bad ESN means they didn't pay their bill or it was an insurance claim on a lost phone and they are blacklisted.
GSM is a technology essentially where it uses a little plastic and electronic card called a SIM card. T-Mobile and AT&T are the two major carriers with this technology. There are several revisions of this technology in use today, GRPS, Edge, and various UTMS and HSPA versions. GRPS is analogous to 1xRTT in terms of speed, and Edge is in between and gives up to 250kb/s down, technically a 3g technology, although not feeling like it. UTMS, HSPA, and WCDMA all refer to a similar type of technology which is what is used by the 3G level of service of AT&T and T-Mobile (fake 4G on T-Mobile). It goes from just faster than Edge to DC-HSPA 42Mbps down speeds and allows for simultaneous voice/data (Edge and GRPS are either data or voice, not both). Your phone number is tied to the SIM card and this technology offers an advantage of if your main phone craps out, you can store your contacts on the SIM and just put it in another phone and still have service.
Roaming and tower authentication are completely different in GSM vs. CDMA. CDMA uses what's called a PRL (Preferred Roaming List) to determine which towers to authenticate to essentially, and sets priority. Some people will "hack" the PRL by changing it so for example if they have Sprint and their tower has the crappy 3g speeds, they roam on Verizon since they have unlimited roaming and get Verizon's better 3g speeds. GSM roaming is set per tower or location on the SIM card, and is a pretty static value dependent on the carrier. Roaming is only if they allow it depending on your plan and location (like T-Mobile prepaid will not roam on AT&T, but postpaid "Uncarrier" plans will).
So what you have is probably a tablet based on the data that gets EVDO service and probably 1xRTT and maybe LTE. If you have it on a phone plan and not a tablet plan, it's probably a Note 2 or something which is just really a phone from what it sounds like if you use Bluetooth. CDMA carriers will only use their devices and lock down ESNs to what they sell, so you can't buy a device from Sprint and put it on Verizon. The exception to that is sometimes prepaid carriers will let you "flash" the phone to their service but don't guarantee the results and don't support it. Examples include Cricket, MetroPCS, Page Plus, and I think Virgin Mobile or Boost *might*, but don't quote me.
LTE is a newer technology which isn't technically 4G yet since we haven't seen speeds here in the US on current LTE revisions of over 100Mbps, but they do have the ability with the right equipment. It uses SIM cards so you will see newer Verizon/Sprint devices actually use SIM cards for service (which is superior as noted above), and have an ESN so it can fall back to 1x or EV. The plan is to eventually roll out LTE to all towers and if you have a LTE device, you use LTE for voice and data (VoLTE), but all carriers don't have LTE on all towers so they fall back to HSPA/Edge or 1x for voice for now. They probably have dual radios like the HTC Thunderbolt and use both at the same time but LTE is still a maturing technology and has a lot of potential.
I hope this helps.
Edit: I forgot to add, for the smaller prepaid plans, you have to look at who they are based off of. Most of them just use a parent network from one of the 4 big carriers (Cricket being the exception, they have their own towers and roam on Sprint if you leave native coverage). I know Page Plus uses prepaid Verizon towers, but for the most part you won't get unlimited uncapped data on Verizon unless you keep your old $30 grandfathered plan. If you switch to a limited data plan, say bye bye. Honestly if you don't want to pay Verizon prices (I don't blame you), and you have the availability for it for coverage, T-Mobile or Sprint have good options. T-Mobile's network where they have 3g/4g is way way good. They just deployed equipment on their towers that's above everyone else with new NSN antennas and the LTE revision is LTE-A I think (check what Milan posted on Howard Forums for sure), but it's high dollar equipment that isn't cheap. Also they are upgrading the backhaul on their towers and most people are pulling between 10-20Mbps on DC-HSPA and 15-30Mbps on LTE. Milan got about 25 Mbps in NYC on T-Mobile LTE so they are a really good way to go and you can get an unlimited plan for $70 a month prepaid. Also, you can get a 5GB/100 min/unlimited SMS plan for $30 from Wal-Mart/tmobile.com.