WARNING: This page is about a different car, the 2010 Pontiac G5 and 2010 Chevrolet Cobalt. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Locating Microphone
Courtesy of GENERAL MOTORS CORP.
Callout
Component Name
1
Mobile Telephone Microphone Assembly Tip:
Remove the microphone bezel by turning and pulling down with light pressure.