Dear developers, when the "lte only" mode is enabled, the phone does not accept calls and cannot ring itself. When switching to the LTE mode, this problem disappears. I ask you to pay attention to this, thank you.
A problem with "Only LTE"
It is not a GOS problem. Your mobile operator must support VoLTE and you need to activate it on the phone.
Alias Please give this a read. Especially Carlos's responses.
Alias Yeah as @Object_11 said, your carrier doesn't properly support VoLTE so you can't make or receive calls over LTE only. Same thing for my carrier, they rely on 3G for calls.