Iphone 4 people can't hear me during calls?

When i make a call or receive a call. The person can't hear me but i can hear him. And when i use viber or record voice on memo the microphone works perfect! What is the solution?

You may not be getting good connection

This is a text book case of 1-way Audio… Its a network issue… Call your carrier and report it… Only they can fix it

Talk louder