This sounds really silly but 2 out of 3 times I end up having a bad conversation because my voice gets muted out by my face hitting dial pad button. So I got more used to making phone calls with speaker phone on & the earphone plugged in. I've tested out my phone's proximity sensor, it is definitely working properly so I think there is something wrong with the way I am holding the phone. By the way I am lefty and use my left hand to pick up the calls. Am I the only one having this problem?