2006 STS with Nav.

Bluetooth connects and when I make a call the radio mutes and I hear the buzz and then there is nothing. The radio stays muted, the call is not dropped, but I can't hear anything and the person I'm calling can't hear me.

Any ideas?

Before you go crazy, pair another cell phone and try it.......................

Try turning up the volume during the call.

'06 are really picky about phones.
Lots of topics on this one, what kind of phone are you using.
I agree with verifying that the volume is turned up, it is separate from radio volume and if you turn it down during a call it will stay down.
I also agree with borrowing someone's phone and pairing it to see how it operates.
That car was only "validated" with 3 devices!

Make sure that you have not selected PRIVATE on the phone screen. That shuts off the speaker and allows you to talk thru the phone while you are in the car.

What really irritates me is I have a Mazda CX-9, and Mazda has a dedicated phone number just for Bluetooth issues and support.

Are you listening Cadillac?