After I experienced the good life with my iPhone, after 2 months of usage all of a sudden the mic stopped working. In the beginning, whenever I had did problem I did a simple reset after which the phone functioned normal again. Though after a while the problem remained and a simple reboot did not resolve the issue anymore. The strange thing was that i was able to make call when I used the headset that comes with the phone.
I tried different things to repair it myself: clean the headphone jack, reboot, reset, and I did a complete re-installation of the software with a DFU (see www.iclarified.com for details).
Finally I decided to bring back to phone to an official Apple store. Unfortunately I live on Aruba, but I was lucky a friend of mine went to Miami the week after. He reported that when Apple heard of the problem, they immediately replaced the phone (maybe the problem was already known with Apple?)
Eitherhow, I own a completely new phone right now, unfortunately with the 2.2.1. software and baseband 2.30 which can not be unlocked by using Yellowsn0w as yet. I have purchased a piggybag Rebel SIM through ebay and I am waiting for it to arrive. By using the Rebel SIM, I should be able to make calls again soon.
Will keep you updated,