iPhone 11 callers say my phone call is breaking up on their end about 25% of phone calls, this did not happen with with my iPhone 6s Plus calling from the same location

Have an iPhone 11 that I bought in June 2021, I had it in an OtterBox case that I bought from eBay, one day when I was talking to my wife on the phone my phone call was breaking up so I took the OtterBox cover off and she said my voice got clear again and it wasn’t breaking up anymore, I thought maybe I had unknowingly bought a counterfeit OtterBox, and maybe that was to blame. I then went on Amazon and make sure I bought one directly from Amazon and it listed that it was from the OtterBox store, it does not have a serial number inside the case but I’m not sure if it is supposed to or not? Anyway it remains to be seen if this fixed the problem but I did notice another person had a similar problem with an OtterBox case and they said they had removed it and things cleared up.. I did see one other person with a similar problem they said they had to do a factory restore but not from the back up and then they restored their apps from an iCloud back up, I guess I could try that? Frustrating! Any suggestions would be appreciated. Thanks