Hello! I have the same problem. I changed the Dock connector, put a plastic on the audio chip, and restored the phone. The microphone isn't working and when I plug in a headset it doesn't work, too. Also it doesn't work with the loudspeaker. Before putting the plastic on the audio chip, the phone had problems with the speaker, too. it interrupted the sound and sometimes I couldn't hear anything. but now it works. just the microphone still doesn't work.
Hi Gilberto, for me, it seems like the lcd is broken. Do change the display assembly. But be really careful while reassembling (at the beginning, when you place the new display on the phone), it's really easy to destroy the digitizer cable. I hope it'll work!