I know this thread is a few months, but I have the very same problem others have posted here. I have a Galaxy s20 Ultra. When I make a call, I hear nothing, no ringing at all. I either get voice mail or the person answers which is surprising because I didn't think it was ringing. I've seen the suggestions for turning off VoLTE, but I don't have that option on my phone for some reason. Any help would be greatly appreciated!