I-Phone 11 garbled voice, cutting in and out

I have been using the iPhone 11 two years. Since the purchase, there are problems with GSM communication. I hear the interlocutor well, but they hear me like a robot. Before that, I used the iPhone 7 Plus for three years, and I had no such problems. My operator is Sprint/Tmobil. I contacted the operator’s support service twice. I have gone to the Apple service center twice and it is still having issues. New sim card, I reset the phone to factory settings. It did not help.

I was waiting for a new iOS firmware, but after installing the latest iOS 14.4.2, nothing has changed. Considering that I am not alone with such a problem as it turns out this is a problem all over the world, I ask Apple to solve this problem, because it is clear that the problem is not in the operator but in Apple devices.