My wife has just had a call from someone on her 32gb iPhone 4 and the caller could not hear her through their phone. They called a few times with the same result. We have since tested her phone calling from a number of different phones all with the same result - she can hear me, she can hear an echo of her voice in the phone but the caller can't hear her at all. However, when she puts her phone on speaker the caller can hear her fine.
Looking at this discussion on apple.com it seems this is a common problem - https://discussions.apple.com/thread/2498579?start=0&tstart=0
She's had the phone for 15 months and this has never been a problem before and it hasn't been dropped etc at all so it's happened completely out of the blue.
Has this happened to anyone else? The phone will be out of warranty, just wondering if anyone would know the best place to take it to be looked at and what the potential cost might be to have it looked at/fixed?