No sound in a call - caused by failure in switching sound profile to Phone Call

I'm using open modem firmware https://github.com/Biktorgj/pinephone_modem_sdk, but suspect, that it is not the problem here (if i'm wrong, correct me).

In a call, there is no audio whatsowever. Like absolute silence. In journalctl, these 2 lines have caught my attention:

kde-telephony-d[3730]: Couldn't set mode 0: Timeout was reached
kde-telephony-daemon[3730]: Failed to set default callaudio mode

If needed, i can provide more logs and testing, as the problem is present on every call i try to make.