I got the same problem even if I am not in 4G Only mode. Outgoing calls are not working but incoming calls are working because the network switches to 3G during the call.
I am using Mobian with Phosh on the PinePhone and found a workaround by changing the network mode from "2G, 3G, 4G (Preferred)" to "2G, 3G (Preferred)" (this is not a good solution for the long term since 3G will be shut down in the future).
Trying to use VoLTE by following information on https://wiki.pine64.org/index.php/PinePhone#VoLTE did not work (but anyway if it is not working, it should switch to 3G like for incoming calls).
Maybe updating the firmware will fix the issue like someone mentioned here (I am using Free Mobile in France with the default modem firmware EG25GGBR07A08M2G_01.001.01.001):
https://wiki.pine64.org/wiki/PinePhone_C...ort#Sweden
The issue is also mentioned here:
https://www.reddit.com/r/pinephone/comme...und_calls/
Update: The issue happened with version 01.002.01.002 and 01.003.01.003 (or versions below) but not with version 30.004.30.004 and 30.006.30.006 (with or without the custom firmware 0.8.0 https://github.com/the-modem-distro/pinephone_modem_sdk).
VoLTE support still needs confirmation on https://forum.pine64.org/showthread.php?...#pid125496.
With the old default firmware, there was also an issue when receiving SMS while connected to 4G, I received it several times indefinitely. The issue does not seem to happen anymore with a new firmware.
I am using Mobian with Phosh on the PinePhone and found a workaround by changing the network mode from "2G, 3G, 4G (Preferred)" to "2G, 3G (Preferred)" (this is not a good solution for the long term since 3G will be shut down in the future).
Trying to use VoLTE by following information on https://wiki.pine64.org/index.php/PinePhone#VoLTE did not work (but anyway if it is not working, it should switch to 3G like for incoming calls).
Maybe updating the firmware will fix the issue like someone mentioned here (I am using Free Mobile in France with the default modem firmware EG25GGBR07A08M2G_01.001.01.001):
https://wiki.pine64.org/wiki/PinePhone_C...ort#Sweden
The issue is also mentioned here:
https://www.reddit.com/r/pinephone/comme...und_calls/
Update: The issue happened with version 01.002.01.002 and 01.003.01.003 (or versions below) but not with version 30.004.30.004 and 30.006.30.006 (with or without the custom firmware 0.8.0 https://github.com/the-modem-distro/pinephone_modem_sdk).
VoLTE support still needs confirmation on https://forum.pine64.org/showthread.php?...#pid125496.
With the old default firmware, there was also an issue when receiving SMS while connected to 4G, I received it several times indefinitely. The issue does not seem to happen anymore with a new firmware.
