iPhone 15 Volume up button not working

If a button or switch isn't working on your iPhone or iPad, here are a few steps that may fix the issue. If they don't, you'll need to set up a repair. Remove any protective films or cases that might block the button or switch. Check for debris or dirt around the button or switch and clean with a soft cloth.

If a button or switch isn't working - Apple Support (IN)

I bought iPhone 15 and when I’m talking on the phone or alarm is ringing if I push the volume up button the phone goes quite and I can’t hear anything or get any volume back at all