I have loaded many different Operating systems and while I can get ATT / Cricket to work well ,I have had no luck what so ever getting any OS to recognize the T-mobile Sim. Tried loading atinout, modem manger and other software to no avail. I am trying to avoid using the modem update software since I don't want to risk trashing the modem. Heck, flashing my Bio makes me nervous. Has anyone found a way around my problem?
Check my post
https://forum.pine64.org/showthread.php?...8#pid85368 for VoLTE settings / modem AT commands, it might help.
I don't have a SIM for an operator that has VoLTE enabled but you should be able to check for yourself (presuming the SIM works on VoLTE with another phone).
There is a "Commercial-TMO_VoLTE" profile in the modem so that would presumably be used automatically if VoLTE is enabled - you can also set it manually yourself.
Hope that helps.
There's also a thread for confirmed 4G VoLTE working here
https://forum.pine64.org/showthread.php?tid=12560 if you get it to work. That should help, too.