I recently just got a Samsung Gravity 3. I've had it for three days and am now experiencing problems with calling people. I receive people's calls, but when I pick up the phone, I am not able to hear the person on the other line. Instead, the person on the other line hears their voice and an echoing sound. They can also hear me talk back, but I am not able to hear them. I have tried resetting the phone, I have made sure that the hearing volume was set all the way up, and I have taken out the memory card and battery to fully restart the phone, but nothing seems to make it work. Any ideas on how to fix this before I have to take it in to the store? Thank you.