First check all the speakers etc just incase there's any debris in them.
I appreciate you can take a call using loud speakers but it's still best to check.
If an area is of low coverage then this can have several effects to a phone call. So does this happen everywhere you go or in a particular area ?
Then when in an active call then use the rocker button to turn up the call volume.
You can run diagnostic tests via your Samsung Members App under the GetHelp section and also via your phone app by dialing *#0*# .
A Samsung Service Centre can also check the phone.
I wish you all the best.
Daily Driver > Samsung Galaxy s²² Ultra 256Gb in Phantom Black.
The advice I offer is my own and does not represent Samsung’s position.
I'm here to help. " This is the way. "