Checking to see if you still need any assistance?
Give these steps below a try, if this doesn't work I would recommend the various service options. You are welcome to speak with your carrier to see what they can offer, you can have Best Buy's Samsung Experience Shop evaluate for software related causes, OR Samsung can help you send the device into an authorized service center to have our technicians evaluate for both software/hardware causes.
For the microphone, there are 3 apps under system apps named Phone, use these steps for each app named phone:
Settings> Apps> 3 Vertical Dots> Show System Apps> Phone> Storage> Clear Cache> Clear Data
Hello everyone, we have updated Sebas's response. Could you give those steps a try? If these steps don't work we would recommend the service options.
Let's try placing the phone in safe mode? It would be a third party app causing the issue. This is how you place the phone in safe mode link.