Wow, you described my problem exactly (audio mute outgoing calls) except maybe it happens more frequently, say 6 of 10 outgoing calls. I am not sure about this frequency because now I switch to speaker and back everytime I call.... In addition, for a period of time (~11/4-11/7) I was getting a 'bad audio reverb' in 1 of 10 of my outgoing calls but it would be fine if I hung up and called the person right back. I bought the ATT 16gb iphone 4s 11/1 and 1 week later put it in an Otterbox Defender case (has a built in screen protector) but it did the 'audio mute' before I had the case. I stopped at an ATT store the 2nd week and described this to the ATT service person and she had already heard about the 'bad reverb' problem an...