I can't hear callers but they can hear me

Having an intermittent issue on my iPhone. Callers can hear me, but I can't hear them. It is happening on outgoing calls too; I will hear the ringing but as soon as the caller answers, I can't hear anything. I've tried the speaker and still can't hear. Disabling Bluetooth doesn't help...the only thing that fixes the issue is a reboot. Then, I can make a call normally again, but it happens again a few hours or days later. Reboot, and it works again.

This was happening with my iPhone 11Pro. I got so frustrated that I upgraded to a brand new, direct from Apple, iPhone 13 Pro. Same exact issue. Makes me think it's an issue with the iOS build (currently on 15.3.1) or its some conflict with an application, but I can't identify any new application that I've downloaded. HELP!!!