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.
Is this some type of joke? User asks for help... given multiple links that are all broken and then the marked Solved answer is his own reply saying that it isn't a Media volume issue, it's an in call volume issue. SMH
This is an issue most users are having since Pie update. As usual... Pie is to blame. My entire phone has suffered low volume across the board. In call volume is low and have to jack the volume to the max which I didn't have to do with Oreo and same with media volume which also has to be jacked to max, where as in Oreo I could have it at around 3/4 volume... which was still sad, but nowhere near as sad as it is now with Pie.