Callers can't hear me.

we just had this issue. We tried rebooting the phone, taking out the battery and updating the software. Nothing worked. Took it into Verizon. Apparently there was a tiny piece of cardboard in the microphone. The Tech took a can of Canned Air to it and it is working fine now.
Occasionally, my caller says it sounds like I'm speaking really low to the point I they can't hear me. When they can hear me perfectly, I can't hear them and it sounds like they are talking with their hand over their mic. I don't know if its a general issue that other people are having, but it's starting to piss me off.
Do the Audio Quality settings here (set to EVRC-B) and see if that helps:

I just got my thunderbolt less than a week ago and i'm also new to this forum(first day). I signed up because I'm having such difficulties when this phone when talking on the phone. Please point to me where in the phone i set to EVRC-B?? I have looked through the phone but couldn't find anything...also I "googled" on how to change it and i read you have to go to programming settings but to be very careful b/c that can ruin the phone. So I wanted to make sure before I went and changed anything.

Also how do i turn the privacy setting off so it doesn't take my voice as a background noise and cancel it out. Any help is greatly appreciated. I don't want to change this phone, it is an awesome phone with so many features!!! but i'm just having lot of difficulties with call quality. By the way, i can hear the other person just fine. Thank you in advance.:)