Acer 4736 — mic problem

respected sir,
subject- mic problem
date- [protected]
i mohammed sameer purchased acer laptop ASPIRE 4736 a month before and i suddenly notice a mic problem when i was gone for voice chat, i come to know it has problem, i can listen the opposite persons voice but he cannot listen my voice properly it was so damaged voice cant understand any thing .i have gone to service center also but they also cant understand the problem.ihave done all the following things which i have told to do
1.i formate the laptop
2 i installed mic drivers from net
3 i have gone to service center thrice
now tell me what should i do to get it done .and i was very upset with your service
now please help me out .
thanking you
sameer