Hi,
I'm looking at changing the firmware on my S7 EDGE from EVR to BTU.
How do I ensure I keep the data on my phone? Will OTA work properly on it when I flash the firmware?
chrissyyyw said:
Hi,
I'm looking at changing the firmware on my S7 EDGE from EVR to BTU.
How do I ensure I keep the data on my phone? Will OTA work properly on it when I flash the firmware?
Click to expand...
Click to collapse
Here you go
https://forum.xda-developers.com/s7-edge/help/change-csc-install-version-via-odin-t3374582
So if I use home csc I can't use OTA?
How do I retain the EE WiFi calling option?
chrissyyyw said:
So if I use home csc I can't use OTA?
How do I retain the EE WiFi calling option?
Click to expand...
Click to collapse
You cannot update via OTA when changing to a different firmware unless it is EVR firmware. If you flash CSC then you can get OTA updates.
The only way to retain the EE Wifi calling is to remain on EVR firmware.
I thought the WiFi calling option worked on BTU but Volte did not?
chrissyyyw said:
So if I use home csc I can't use OTA?
How do I retain the EE WiFi calling option?
Click to expand...
Click to collapse
I'm from xsg CSC, I flashed mm via Odin with BTU firmware and home_csc also from BTU firmware. I registered to beta programme and got update, now I'm on stable nougat.
★hasibgns★
Was the update using OTA?
chrissyyyw said:
I thought the WiFi calling option worked on BTU but Volte did not?
Click to expand...
Click to collapse
I have BTU factory unlocked and unbranded device and I can confirm wifi calling works on EE. Just enable it in the settings.
I debranded mine from Virgin UK to BTU, I have no wifi calling options although it doesn't bother me as I don't use it anyway.
lyriquidperfection said:
I have BTU factory unlocked and unbranded device and I can confirm wifi calling works on EE. Just enable it in the settings.
Click to expand...
Click to collapse
Which firmware are you running G935FXXU1BPLB??
When flashing from EVR to BTU, what items should be selected?
BL, AP, CP, CSC (or CSC home)? I'm not fussed about VoLTE as EE keep having outages, however I do need WiFi calling. I tried flashing Nougat last night and selected BL, AP, CP and CSC but WiFi calling option was gone from settings
Thank you
red_snow said:
When flashing from EVR to BTU, what items should be selected?
BL, AP, CP, CSC (or CSC home)? I'm not fussed about VoLTE as EE keep having outages, however I do need WiFi calling. I tried flashing Nougat last night and selected BL, AP, CP and CSC but WiFi calling option was gone from settings
Thank you
Click to expand...
Click to collapse
I have recently flashed the BTU Nougat firmware and can confirm that I am able to use WiFi calling on EE
Flash AP, CP, BL & CSC (or CSC_HOME if you want to retain data but may cause some issues)
Wonderful, thanks for confirming. I've downloaded BTU 7.0 and EVR 6.0.1 from sammobile so I guess my steps are:
1. Full backup of my S7 Edge (EVR 6.0.1) with Smart Switch
2. Remove SD card
3. Flash BTU with BL, AP, CP and CSC
4. Full reset/erase
5. Test WiFi calling, presume it's in the dialler settings still
6. Restore data/apps with Smart Switch
7. Check for any OS/App updates
8. Have a cider
Sound good?
BTW, when I last had a go at flashing BTU 7, there was no WiFi calling in the dialler settings Hopefully it'll work this time and at some point, EE will allow VoLTE (if IMS doesn't keep falling over).
Cheers
I can't find any WiFi calling options in settings on BTU 7 which I flashed over my EVR.
Interesting, that is why I'm reluctant to do it again. I've heard it work for some and others say flash with BTU 6.0.1 and then OTA to 7.0
Not that WiFi calling matters again now as EE have yet another IMS issue, no WiFi calling or VoLTE ....... AGAIN!
red_snow said:
Interesting, that is why I'm reluctant to do it again. I've heard it work for some and others say flash with BTU 6.0.1 and then OTA to 7.0
Not that WiFi calling matters again now as EE have yet another IMS issue, no WiFi calling or VoLTE ....... AGAIN!
Click to expand...
Click to collapse
What is this IMS issue you're talking about?
Anyways, I've had VoLTE working since the Nougat ODIN files became available.
Flash official Nougat files + BETA 1 CSC (Nougat OXA) and Wi-Fi Calling and VoLTE works fine.
The IMS (IP Multimedia Subsystem) is the tech stack that allows for VoLTE and WiFi calling over 4G.
Regarding your method of retaining VoLTE/WiFi calling, I like it. Where can I download the beta firmware from in terms of a reputable site?
Incidentally, do you know which beta version stopped VoLTE on EE?
red_snow said:
Wonderful, thanks for confirming. I've downloaded BTU 7.0 and EVR 6.0.1 from sammobile so I guess my steps are:
1. Full backup of my S7 Edge (EVR 6.0.1) with Smart Switch
2. Remove SD card
3. Flash BTU with BL, AP, CP and CSC
4. Full reset/erase
5. Test WiFi calling, presume it's in the dialler settings still
6. Restore data/apps with Smart Switch
7. Check for any OS/App updates
8. Have a cider
Sound good?
BTW, when I last had a go at flashing BTU 7, there was no WiFi calling in the dialler settings Hopefully it'll work this time and at some point, EE will allow VoLTE (if IMS doesn't keep falling over).
Cheers
Click to expand...
Click to collapse
Sounds good, but I'd change step 8 to a lager!
red_snow said:
The IMS (IP Multimedia Subsystem) is the tech stack that allows for VoLTE and WiFi calling over 4G.
Regarding your method of retaining VoLTE/WiFi calling, I like it. Where can I download the beta firmware from in terms of a reputable site?
Incidentally, do you know which beta version stopped VoLTE on EE?
Click to expand...
Click to collapse
I flashed the latest official BTU firmware with Odin and have been using WiFi calling for 24 hours without a hitch.
The firmware can be downloaded HERE
CuBz90 said:
Sounds good, but I'd change step 8 to a lager!
I flashed the latest official BTU firmware with Odin and have been using WiFi calling for 24 hours without a hitch.
The firmware can be downloaded HERE
Click to expand...
Click to collapse
Where is the option for it in settings!?
Chris_c81 said:
Where is the option for it in settings!?
Click to expand...
Click to collapse
Open Phone app > Settings > Scroll right to bottom to find wifi calling
Related
OK, I flashed my G935FD dual sim with G935FXXU1BPH6_G935FVFG1BPH1_VOD ( I did AP BL CP CSC), it rebooted did a couple of OTA updates, has wifi calling enable, but still wont wifi call, or go into wifi calling mode.
After the flash and OTA's I checked the versions and have :
AP G935FXXS1BPJ1
CP G935FXXU1BPHJ
CSC G935FVFG1BPH1
this is exactly the same as my UK Vod shop purchased G935 single sim, which obviously does go into wifi calling mode
One minor point, my G935FD dual sim phone receives messages dfrom VOD after a sim change stating auto configuration of APN is not possible, is VOD UK still detecting my dual sim device and disabling wifi calling
any ideas anyone pls, has anyone got WiFi Calling to work on 935FD for Vodafone?
cheers
(oh, also tried G935FXXS1BPJ1_G935FDBT1BPH2_DBT.zip and didnt even have the wifi calling check box )
I have mine working on the att version
VissGaming said:
I have mine working on the att version
Click to expand...
Click to collapse
cool, I have heard from other ATT or UK EE users who have made this work easily, just no vodafone users
update here from me :
Having tried many roms, with no success, I reverted back to a UK VOD ROM, as this was a multi CSC ROM, which defaulted to VOD2 CSC (Germany I think), I rooted the device and changed the CSC to VFG (VOD UK I believe)
Still no wifi calling, though it is enabled in the CSC and onmy account I dont have the check box under phone settings -and have no idea how to force it to appear.
Any ideas pls, has anyone successfully got WiFi Calling to work for Vodafone (UK ??) on a 935FD ?
surfnsnack said:
cool, I have heard from other ATT or UK EE users who have made this work easily, just no vodafone users
Click to expand...
Click to collapse
I am interested in getting a dual sim version of the s7 edge to use with EE in the UK. Could you please elaborate on compatibility with EE's wifi calling? Did you read about it in some forum? Do you know people who have tried it? Do you know exactly which versions are compatible (935FD, 930 , etc)? Thanks!
surfnsnack said:
OK, I flashed my G935FD dual sim with G935FXXU1BPH6_G935FVFG1BPH1_VOD
Click to expand...
Click to collapse
So you flashed a single-sim firmware (for G935F) onto a dual sim phone (G935FD) and it worked? Did you retain dual sim functionality?
cdl2 said:
So you flashed a single-sim firmware (for G935F) onto a dual sim phone (G935FD) and it worked? Did you retain dual sim functionality?
Click to expand...
Click to collapse
Yes flashing firmware for the G935F retains Dual SIM functionality, mine is flashed with the BTU firmware as UK s7 version
@copex , thanks! Are you on EE? Have you had a chance to verify if wifi calling works?
Also, is there any particular way to flash the firmware with Odin? Or shall I just follow one of the many guides on the web?
I don't need to be rooted, right? I don't want to root because otherwise I won't have access to my work email.
cdl2 said:
@copex , thanks! Are you on EE? Have you had a chance to verify if wifi calling works?
Also, is there any particular way to flash the firmware with Odin? Or shall I just follow one of the many guides on the web?
I don't need to be rooted, right? I don't want to root because otherwise I won't have access to my work email.
Click to expand...
Click to collapse
I am on EE but via Plusnet mobile and they do not support wifi calling, i used Odin to flash the device as i changed the CSC to BTU i done a full wipe so i could get OTA updates, i followed the info here.
https://forum.xda-developers.com/s7-edge/how-to/official-stock-firmware-update-odin-t3335065
i used SamFirm_v0.3.6 to download the uk firmware
copex said:
i used Odin to flash the device as i changed the CSC to BTU i done a full wipe so i could get OTA updates, i followed the info here.
https://forum.xda-developers.com/s7-edge/how-to/official-stock-firmware-update-odin-t3335065
Click to expand...
Click to collapse
What do you mean exactly when you say you changed the CSC? When you ran Odin, did you load all 4 files: BL, AP, CP, CSC ? Specifically, did you load the CSC file or the Home_CSC file in the CSC box?
Thanks a lot!
On a different note, where were you able to buy a dual sim s8?... all the ones on Amazon come with a clear "no Warranty" disclaimer.
I am not sure dual sim S8s are out yet - we were talking about the s7 edge. These dual sim phones can typically be bought in countries like the United Arab Emirates or Hong Kong, or on ebay, but if you buy from there and bring the phone to Europe or the US it basically means no warranty. There are also lots of small websites that sell them, but I wouldn't even consider them unless they support the paypal guarantee - who are you going to sue if they don't send you your phone?
cdl2 said:
What do you mean exactly when you say you changed the CSC? When you ran Odin, did you load all 4 files: BL, AP, CP, CSC ? Specifically, did you load the CSC file or the Home_CSC file in the CSC box?
Thanks a lot!
Click to expand...
Click to collapse
when you download the BTU firmware there are two CSC files one will allow the phone to update and keep the data and the other will wipe the phone and you will lose all of your data, when you change the CSC region you have to do a full wipe to get OTA updates, if you upgrade the OTA updates will stop if the CSC region is changed
you have to flash all 4 files.
the csc file i flashed was CSC_BTU_G935FBTU..................................... if i remember correctly the CSC_HOME............... is the one that updates the phone
I'm sick of waiting for firmware updates for official EE firmware, BTU has had 2 since EE's firmware was last updated and that's not including the Nougat beta updates.
Has anyone got VoLTE working on EE using BTU firmware?
Works on Nougat beta, BTU, UK EE, wifi calling too
liamstears said:
Works on Nougat beta, BTU, UK EE, wifi calling too
Click to expand...
Click to collapse
In the latest beta volte does not work. Samsung disabled it becuase ee does not want people with unbranded phones or phones which have not been purchased from them directly to have the volte feature.
amar95353 said:
In the latest beta volte does not work. Samsung disabled it becuase ee does not want people with unbranded phones or phones which have not been purchased from them directly to have the volte feature.
Click to expand...
Click to collapse
Really? That's disgusting behaviour on behalf of EE. When the S8 comes out i'll only be one year into a two year contract so will probably end up buying it outright in which case it will be unbranded and if I can't use VoLTE i'll be seriously pissed off.
chipxtreme said:
Really? That's disgusting behaviour on behalf of EE. When the S8 comes out i'll only be one year into a two year contract so will probably end up buying it outright in which case it will be unbranded and if I can't use VoLTE i'll be seriously pissed off.
Click to expand...
Click to collapse
I'll be in the same boat. I always buy my phones outright and use a sim only contract I hope EE change their decision because in the week I had volte available to me in the android n beta it made a huge difference. The call was clearer and I could still search the web at full 4g Speed.
I assume right now, if you flash the s7 edge within EE firmware from sam mobile volte works fine ?
I'm on btu right now, tried the nougat beta and on beta 2 volte works fine on EE, but since beta 3 and beta 4 they stopped it.
So I'm thinking of flashing EE firmware.
I use BTU firmware with my original EE CSC and I have VoLTE working fine
How can you check it's working Fine? I got my phone from carphone warehouse. Sim free and no volte settings?
Sent from my SM-G935F using XDA-Developers mobile app
You need to have the EE firmware installed as far as I can tell. Only devices purchased directly from EE have the feature available.
StevenAFC said:
You need to have the EE firmware installed as far as I can tell. Only devices purchased directly from EE have the feature available.
Click to expand...
Click to collapse
can you flash from BTU to EE firmware and have it working?
OK I know it's taken a while, but for no reason and without me changing any settings, a VOLTE icon has just appeared on my top notification bar. I am running BTU which was flashed when I first bought the phone (SM-G935FD model) CSC changed as well, had a few OTA updates including the Nougat 7.0 January Security Build. I am on EE btw. I still can't find any settings to switch it on or off, but at least I have it now.
TraumaTiger said:
OK I know it's taken a while, but for no reason and without me changing any settings, a VOLTE icon has just appeared on my top notification bar. I am running BTU which was flashed when I first bought the phone (SM-G935FD model) CSC changed as well, had a few OTA updates including the Nougat 7.0 January Security Build. I am on EE btw. I still can't find any settings to switch it on or off, but at least I have it now.
Click to expand...
Click to collapse
What is your CSC in phone info?
There you go guys. Tested. working perfectly
https://forum.xda-developers.com/s7-edge/how-to/finally-method-enabling-volte-s7-edge-t3553066
is this still valid if i have LATEST FIRMWARE draa?
Hi everyone,
I installed following U firmware on my G935P with T mobile CP from latest G935T firmware. Everything works great (including WiFi calling) but VoLTE is not working. There is option in settings > networks to enable HD voice calling but enabling it doesn't help. I dont have any option for VoLTE prefereed in Phone Menu. I even tried enabling with QuickShortcutMaker to enable VoLTE. but doesn't do anything, I cant see HD logo while making calls or VoLTE symbol.
Country / RegionUSA (T-Mobile)
PDA : G935UUEU4BQH3
Product Code : TMB
CSC : G935UOYM4BQH3
Phone : G935UUEU4BQH3
http://updato.com/firmware-archive-select-model?record=657F3693929911E7963AFA163EE8F90B
Can someone tell me what I am doing wrong ?
You have to flash the T-mobile csc to get volte working I believe.
Is that confirmed? I didn't realize we could mix and match CSCs.
Thanks
VoLTE does not work with the U firmware.
No you cannot use the Tmobile CsC, if you want your phone to boot. You can use the Tmobile radio aka the CP file
bsharp8 said:
You have to flash the T-mobile csc to get volte working I believe.
Click to expand...
Click to collapse
Sorry, But you can not flash another ROM CSC as it contains firmware details. Odin will flash without error, but your phone will not boot. and you will see the broken android error in recovery.
masterhuh said:
Is that confirmed? I didn't realize we could mix and match CSCs.
Thanks
Click to expand...
Click to collapse
As @justda mentioned, No you can not mix and match CSS with different ROM. Only CP files are interchangeable between Snapdragon Models. You should use CP file from your carrier latest firmware to get better signal and more band support.
justda said:
VoLTE does not work with the U firmware.
No you cannot use the Tmobile CsC, if you want your phone to boot. You can use the Tmobile radio aka the CP file
Click to expand...
Click to collapse
I read on some threads where OP mentioned working VoLTE and WiFi calling for At&t, so I thought it should be work for T mobile too. Let me know if anyone has a solution for this problem, I am also in the same boat.
https://forum.xda-developers.com/att-galaxy-s7/how-to/xda-community-love-g930u-t3415875
https://forum.xda-developers.com/att-galaxy-s7/how-to/how-to-flash-firmware-att-volte-video-t3447225
nicsptl said:
Sorry, But you can not flash another ROM CSC as it contains firmware details. Odin will flash without error, but your phone will not boot. and you will see the broken android error in recovery.
As @justda mentioned, No you can not mix and match CSS with different ROM. Only CP files are interchangeable between Snapdragon Models. You should use CP file from your carrier latest firmware to get better signal and more band support.
I read on some threads where OP mentioned working VoLTE and WiFi calling for At&t, so I thought it should be work for T mobile too. Let me know if anyone has a solution for this problem, I am also in the same boat.
https://forum.xda-developers.com/att-galaxy-s7/how-to/xda-community-love-g930u-t3415875
https://forum.xda-developers.com/att-galaxy-s7/how-to/how-to-flash-firmware-att-volte-video-t3447225
Click to expand...
Click to collapse
My apologies to everyone. Thanks for correcting me before someone screwed their phone up. :good:
Just out of curiosity. Did anyone use 935U firmware, but XAA instead of TMB? For me, with XAA, VoLTE and wifi calling worked out of the box as soon as I inserted my T-Mobile SIM.
walrusmonarch said:
Just out of curiosity. Did anyone use 935U firmware, but XAA instead of TMB? For me, with XAA, VoLTE and wifi calling worked out of the box as soon as I inserted my T-Mobile SIM.
Click to expand...
Click to collapse
Flashing latest U firmware with T mobile CP fixed issue for me. I can confirm VoLTE for t mobile works on U firmware out-of-box with or without T mobile CP(radio). @walrusmonarch thanks until now my phone was on U firmware with July security patch. Not sure why it was not working, it's a used phone and the previous owner also made some rom related changes .
Btw, As per my knowledge, both firmware contains the same MULTI-CSC
(i.e. "CSC_OYM_G935UOYM4BQH3_CL12006533_QB14665430_REV02_user_low_ship_MULTI_CERT"). As per sim card inserted during first boot the phone will reset CSC code to match carrier. In my case, it will automatically switch to TMB, even if I use U firm with XAA default code as it contains the same AP, CP, BL and multi-csc file. correct me if I am wrong.
I am on Telus and bought a USA phone. I have flashed the updates using Odin and the HOME_CSC so that it could be carrier set to Telus.
However, it still does not get wifi calling and volte even though I've had the carrier enable it too. The CSC did enable HD voice though.
My question is whether I can flash the offical Telus firmware on my phone as the hardware looks to be the same.
I believe I will need the modded Odin but just wondering if anyone has had success with other models rom on their phones.
[Guide] Enable Video Calling, HD Voice, & More - Unlocked Note 8 With T-Mo (Oreo / N)
There is a fairly simple way to enable T-Mobile features while using a N950U1 (unlocked) firmware while on T-Mobile.
*We are going to use two example firmwares from the latest Oreo release, N950U1UEU3CRC1 & N950USQU3CRC2., this can be done with older firmware just get firmware from around the same date.
1. Download both of the latest firmware for the N950U & N950U1.
2. Open Odin 3.13.1 and boot the phone into Download Mode
3. In Odin, Load the BL, AP, & CP from the N950U1 firmware (N950U1UEU3CRC1) but load the CSC from N950U (N950USQU3CRC2) (Do not use one labeled home)
3. Reboot, enjoy N950U1 with T-Mobile features and icons.
Will this retain or wipe data???
DeeXii said:
There is a fairly simple way to enable T-Mobile features while using a N950U1 (unlocked) firmware while on T-Mobile.
*We are going to use two example firmwares from the latest Oreo release, N950U1UEU3CRC1 & N950USQU3CRC2., this can be done with older firmware just get firmware from around the same date.
1. Download both of the latest firmware for the N950U & N950U1.
2. Open Odin 3.13.1 and boot the phone into Download Mode
3. In Odin, Load the BL, AP, & CP from the N950U1 firmware (N950U1UEU3CRC1) but load the CSC from N950U (N950USQU3CRC2) (Do not use one labeled home)
3. Reboot, enjoy N950U1 with T-Mobile features and icons.
Click to expand...
Click to collapse
Sent from my SM-T820 using Tapatalk
Odin wipes data.
Backup your data with your favorite backup/restore method/s before using Odin. So have the data to restore later with your favorite backup/restore method/s afterwards.
Nice. Going to try on my T-Mobile Note 8. Just to confirm what bloatware is installed by using the T-Mobile CSC file? I'm looking to get rid of all the T-Mobile bloat while still having the video call feature working
Sent from my SM-N950U using Tapatalk
Will this trip knox?
I have no idea what is Odin and where do i get it?
Do some research. Watch some YouTube videos about rooting your phone. Then do some more research.
We are all here to help each other. That's what XDA is about
Odin thread below
https://forum.xda-developers.com/showthread.php?t=1372414
Sent from my SM-N950U using Tapatalk
So, I need to root to flash this, right?
Sent from my [device_name] using XDA-Developers Legacy app
Wicked68 said:
So, I need to root to flash this, right?
Sent from my [device_name] using XDA-Developers Legacy app
Click to expand...
Click to collapse
Nope. This is official Samsung firmware. No root needed and it won't break Knox.
I actually did this the other day but after flashing the U1 firmware on my T-Mobile Note 8 using the patched Odin I then used the regular Odin and just flashed the CP and Userdata from the T-Mobile U firmware and it enabled RCS, Video Calling, VoLTE, Wifi Calling and did not install any bloatware. Everything is perfect
Sent from my SM-N950U using Tapatalk
Vish.N said:
Nope. This is official Samsung firmware. No root needed and it won't break Knox.
I actually did this the other day but after flashing the U1 firmware on my T-Mobile Note 8 using the patched Odin I then used the regular Odin and just flashed the CP and Userdata from the T-Mobile U firmware and it enabled RCS, Video Calling, VoLTE, Wifi Calling and did not install any bloatware. Everything is perfect
Sent from my SM-N950U using Tapatalk
Click to expand...
Click to collapse
Oh, ok, cool. I have unlocked and using on T Mobile, I have wifi calling and the like already. Since the new update, video calling was removed again. I don't even use it, but I still want the feature activated. I expected the unlocked version to have everything, not be missing features. Thanks
Sent from my [device_name] using XDA-Developers Legacy app
Does this unlock your phone?
foriesg said:
Does this unlock your phone?
Click to expand...
Click to collapse
Nope. Just the firmware change. SIM will still be locked. You'll need a unlock code or carrier to unlock it
Sent from my SM-N950U using Tapatalk
What happens when you install an update, does that mess anything up?
I have an sm-n950u with the crf3 update. Can I use this without harming anything?
Will this same method work if I have the unlocked Note 9 and I want to have AT&T features?? Do I just flash the CSC from the AT&T firmware and keep everything else the files from the U1 firmware?
I just flashed the U1 firmware on my Verizon note 9 to get the Verizon crap off of it because I have At&t but I realized that it isn't as perfect as I thought it was because I have no HD voice or Video Calling. Thank you!!
Only thing I dont like about this is that it does at the t mobile splash screen on boot up/shut down
What else gets unlocked? I already have WiFi calling.
I'm considering doing this "franken-flash" with the latest PrinceCosmy Odin on my 935U, but have the following questions (I know it's a 950U thread, but should be similar):
1. Will I still get OTA updates & are they safe? Has anyone tried a manual update?
2. If so, what should I expect; would BL & AP eventually flash to the T-Mobile variant or would each component (BL, AP, CP, CSC) follow it's own upgrade path?
3. Will it also fix the problem of T-Mobile forcing OTA updates to be done over WIFI? (happened the last 2 updates)
Here's the features I'm expecting to fix:
Flashing 935T CSC - Enable Video Calling, HD Voice, & RCS (pros), add T-Mobile bootup splash (big con)
--NOTE: VoLTE setting is available & turned on but doesn't appear to fully enable HD Voice; WifiCalling is already functional
Flashing 935T CP - Enable 4x4 MIMO & 256/64 QAM (huge pros), possibly lose roaming use of a few bands (2G CDMA: CDMA800, USPCS1900; 3G CDMA: BC0(800), BC1(1900), BC10(800); UMTS: B8(900); 4G FDD LTE: B13(700), B25(1900), B26(800), B29(700), B30(2300)) (con)
Flash any mixture - possibly break OTA updates (con); accidentally take an OTA update while mixed & brick phone (huge con)
I first called T-Mobile & asked if they could edit the IMS settings to enable Video calling. After elevation to tech support & some further discussion I was eventually told "it's not a T-Mobile phone so you're out of luck - call Samsung". Of course that'd be a waste of time since it's probably T-Mobile that locked out the IMS settings in the first place.
In case anyone needs them - I got the latest firmware direct from Samsung using SamFirm (pretty fast downloads). T-Mobile is the TMB "region"; that works fine with both SM-G935T and SM-G935U models & set to "auto" to get the latest.
in theory would this method work with the s8+? (with the s8+ firmwares, obviously)