Samsung Guru 1200- outgoing sound - voice hearing problem?

i have a basic phone just to enjoy tariff plans from uninor. But after two weeks of purchasing i am facing a problem regularly. The problem is when two people are there is a conversation the one who is talking from Samsung Guru E1200 unable to hear properly and on the other hand voice doesn't reach clearly.

I take it to the service center to get it repaired they said mike is not working properly. After the replacement of mike, it is giving problem back to back again. I am totally fed up what to do?

Buy a new phone..

Ok jokes apart, are you sure there is no network issue or may the place you are using phone has some electrical / magnetic interference.