i got an iphone on february and it's unlocked, because I use it in estonia. A week ago started problems with calling and receiving calls. If somebody calls, i answer and it's totally quiet. I can't hear anything and the other part also can't. I haven't dropped my iphone and it also hasn't got wet. Sometimes after i've blown some air to the headphone output, i can make a call and hear again, but soon the problem continues. what could be the problem and how could it be fixed?