[Sony Xperia XZ2 Compact Guides, News, & Discussion] depsilon:
XZ2C H8314 VoLTE working on T-Mobile USA

Yes VoLTE works but no VoWIFI with the following method:

Download USA Customized for XZ2C (H8314) and use only the two oem...sin files from XZ3 (H8416) USA Customized. (overwrite the two files in the XZ2C stack)

Use newflasher tool. (I deleted all .ta files and userdata file to avoid losing existing data)

To put the phone into flash mode, power off, hold the vol down button and plug in your usb cable while holding the button until you get a dim green light.

The device will show up in device manager under USB and you can run newflasher as administrator. Please search for a tutorial - there are many that are very good with screenshots of the files you want to move into the newflasher folder.

Some hangups I ran into when setting up and flashing -

Installing flashtool drivers required disabling driver signature enforcement on win10 (Flash device did not show up in usb in device manager until this was done)

For safety, after the flashtool driver install, I performed a repair on xperia companion app in case of any driver conflicts.

Running newflasher again, I got an error: Unable to open ./boot/Apollo_XBootConfig_MiscTA.ta! after multiple system files had been flashed.

But not to worry, the command window said the phone exited flash mode, but got error 933 - unable to sync. - No worries though, just make sure the command window states the phone is out of flash mode somewhere, disconnect your cable and power up your phone.

Then you will get an android message saying your carrier settings will update after reboot and the phone may reboot.

Once rebooted, enter *#*#4636#*#* in your phone dialer app (Takes 30 seconds after fresh boot for the menu to come up) , select phone information, and select LTE only (Note: VoLTE Provisioned will have the slider set to the right, but grayed out - Before the re-flash, the slider was set to the left and grayed out), reboot again. (If you click the 3 dots and look at IMS Status, you will see IMS status Registered, VoLTE Available and UT interface Available - Before the re-flash status was not registered and not available)

Now when you make a call, it will say "HD" in your dialer while on a call and your signal indicator will no longer say 3G when calling.

VoWIFI does not work, but you can use whatapp or something else like googleFi if its a must have, but in my case, I did not want to have to buy a new phone in January when they turn off 3G - Phones are too darn big now anyways and I love the display on this phone.

Notices will go out starting AUG 4th if your phone is marked as not supported using T-Mobile IMEI BYOD online tool - Their tool said my phone does not support VoLTE (Not fully true - It just does not have Band 71 for Long Range VoLTE but will use Band 4(66) just fine, I cannot confirm band 12 even though the phone spec supports it. It appears only Short range VoLTE is working on the phone unless someone else can confirm with this method, My Band 12 tower is behind a hill and i am 20 miles from it) T-mobile currently does not have a whitelist like AT&T, so If the UE (User Equipment - ie. phone) is configured properly, the network will handle the rest. I hope this practice does not change.

The advantage to using this method, is you are using completely stock USA files - My bootloader is locked and i am not rooted BTW. My XZ2C is only carrier unlocked.

The build number of both Roms I used was the same 52.1.A.3.49 XXX - Good Luck.

BTW - Some people were asking what modem config is working with VoLTE on T-mobile USA - to get the modem setting type *#*#7378423#*#* and in the service menu select software info, under Current modem config the value reads:

row/tmobile/vl/us