i want to ask about make a call in iphone.. iphone 3gs.. firmware 4.0.1. my problem is when i want to make a call, the conversation just only 10sec.. after that it will end / auto disconnect.. but second / third time i make a call i can call more than 10 sec or like a normal..

have anyone had this problem like me?? and how to solve it?? can someone help me..