iPhone 11 Pro Max randomly switches to speaker

While I'm on a call my iPhone Pro Max will randomly switch to speaker and blast out my eardrum. I'm running the latest software and I've taken it to the Apple Store. But they seem bewildered by the problem. They said my hardware tested OK and so did my software. They erased everything and reloaded my software, but frankly I'm afraid to test it to see if it works or not. My left ear feels like there's a grape in it, and all sounds are all muffled now. I'm afraid if it gets hit with another blast from my speaker, it will mean the end for that ear. I'm afraid to use my other ear to test it because it's the only good ear I have left. So I only use my iPods or my bluetooth earpiece. But I shouldn't have to use those indefinitely for a $1000 phone to work. I've aways had iPhones, iPads, Mac Book Pro's, Apple Watches. You name it. I am a total "Apple Geek" and I've never had this issue with any other iPhone I've ever had. I can't believe I'm the lone ranger here. I'm thinking there's got to be other half deaf iPhone 11 users out there. How do I fix this before I'm seriously in need of some Beltones?