I only seemed to have this issue when I'm talking with my wife(Not trying to be funny here). She has a loud voice and even though I did the same thing you did by turning the in-call volume all the way down, I still could still hear her very clearly(louder than others). So I just instructed her to turn down the in-call volume on her phone and then everything was fine. If this is happening to you with all calls, I would suggest you take the phone back to Verizon and have them look into the issue. Hope this helps.