iphone 11 ringing ringing volume goes down on first ring

I have an iPhone 11 from ATT. About a week ago, the volume level started automatically dropping itself when calls come in. The volume level also drops itself automatically at times and it is hard to hear texts coming in. I can't figure out what is going on. If the phone is in my pocket I feel the vibration. I have ATT Assurion support, but they are useless. The techs are clueless compared to Apple and i feel they are not trained and don't even try very hard. They keep wanting to replace my phone. Every time I call, I just ask them if they would help me search for the problem. I have replaced this phone once (with Insurance from ATT) and they charged me a deductible of 200.00. I don't want a phone replacement again, and get billed.

I have looked at all avenues. I have disconnected the phone from my sound bar and smart TV. The only bluetooth option is my car outside and it is not turned on. This problem has also happened when I was not near any vehicles, or other potential blue tooth sources. I have also gone though looking at volume levels in "phone" and sounds and haptics and the volume level is set to its highest setting.

Anyway, is there anyone in the community that knows why this happens?