HTC 820s Mic problem

[AC Question]

I'm using htc 820s .and facing Mic problem. The caller can't hear my voice.I have repaired with htc authorized service centre 4times..but the problem still continues. last time they said they have changed main mother board.but stil I'm facing theproblem frombthe very next day I have recived from htc service centre. Somebody pls tel the solution