I am having the exact same problem! People say I sound as if I am under the sea! I had a brand new A12 for a while, then dropped it, got a recon one from Tesco & no one can hear me. SO frustrating. It's a new SIM too, so that is not the issue. I think it is an issue with this model itself. Am going to take it back to Tesco to see if they can help - but not holding my breath! And for me it is so unnatural to be speaking into the bottom of the phone! I am a hearing aid user and I constantly have to move the phone around so I can hear properly, then move it back so I am speaking into the bottom - and STILL.cannot be heard! Grrrr!