My Z830 mic isn't working. It is less than a year old. It doesn't matter if the call is incoming or outgoing, the recepient cannot hear me, but I can hear them. I don't have the mute button on and the volume is all the way up. I've shut it down, removed the battery and turned it back on, but the problem perists. How can I correct this problem? The store I bought it at said they couldn't do anything for me (frustrating).