iPhone 14 Pro Ringer Volume

My new iPhone 14 Pro ringer volume will not stay on. I adjust it up to max volume and also go into settings to adjust it to NOT be able to be changed using iPhone buttons. Every time I look at my iPhone the volume is back at zero! This happens every repeatedly - every time I reset the volume and check about an hour later to see if I’ve received the call I’d been waiting on, I find the volume back at 0 and again I’ve missed my phone call! I’m at the point of needing to return the phone as I can’t fix the problem and can’t afford to miss all of my calls. Please HELP!