Q: I can barely hear the person on the other end when making or receiving calls. music and ringtones work fine. Any suggestions?

Hi. Check this article : If you can't hear a person on a call or voicemail or if the sound quality is poor on iPhone - Apple Support

Try to reset your device. This won't delete your data stored on this device.

• Press and hold the Sleep/Wake button
• Press and hold on the Home button
• Keep holding both buttons until the display turns off and back on with Apple logo on it.