Really the only options you have are reset and restore. You said a reset didn't work so try a restore; probably should do it as new.
If that doesn't work then you will have to call Apple support or take it to a store to have it checked out. They will reset it again and restore it again to ensure you were capable of doing those yourself and then if that doesn't work they will replace it. Sorry.
You could get a voice recorder app from the app store to test if the microphone is working, or try a voice search with Google Mobile app if you have that.