No sound during phone calls? Here are a few solutions you can try;
1: Clean the receiver of iPhone
If your iPhone is exposed to dirt and dust, cleaning the receiver slot helps with the sound.
2: Turn up the volume
Just in case you have lowered the volume by mistake.
3: Check the Bluetooth
Make sure there aren’t any wireless speakers connected through Bluetooth. Go to setting, Bluetooth and toggle Bluetooth off.
4: Reboot iPhone
Rebooting your iPhone can solve most problems.
5: Erase All Content and Settings
As a last resort, Reset your iPhone. Make sure to take backup of your phone before a reset.