My brother gave me his M7 after OTA update soft bricked the phone(he was on stock). My only recovery option at the time was a custom rom. Now no one can hear me when I answer or make a call, I have to use the speaker phone(which is crystal clear). It's like the mic is Muted/turned off during calls. Both mics work fine, I've tested using Voice recording software, so there is nothing physically wrong with either mic. I have google extensively & there doesn't seem to be any real option except a replacement phone. Best guesses so far is interference with "Noice Cancelling Software" interference & mainly for USA carriers. Any kiwis had a similar problem or with a possible solution?.
I'm going to try a Kitkat rom tomorrow & i also found a Aussie stock rom the works with NZ carriers which I'll also try.