iPhone 5 bad call voice quality

Got the new iPhone 5 and have bad phone call quality. The recipient of the call seems to be able to hear me ok, but their voice either isn't there or drops out or sounds grainy like when you have bad cell reception. Many times, the calls have just not connected. I know that that my cell reception and the recipients cell reception were excellent. This has occured when calling other cell phones, land lines, and toll free numbers. Anyone else having this issue? Have an appointment at Apple tomorrow morning to see what they think.