MUTE BUTTON

Hello,

Hmm, try these steps:

1) Restart the phone

2) If your phone has a case on it, remove it

3) Check for lint or debris around the mute button

4) Slide the mute button back and forth a few times

5) See this: How to put your iPhone on vibrate, ring, or silent mode - Apple Support

6) If no help, describe your exact symptoms in more detail

Good luck.