Microphone issues

My husband received an iPhone 4 and the microphone is not working - right out of the box from the warehouse. Does anyone have a fix? (We tried resetting.)

We're hoping we don't have to return it but if it's inevitable, we will. Just hoping to find someone whom may be able to offer help before we go to the trouble.

I'm always raving about Apple products and when he finally gets one, it's faulty (Fail). :-/