"I can answer incoming calls..."
Please clarify. For example, do you mean that, you can call your Google Voice number from some other telephone number (NOT from your forwarding phone number), and you see the blinking right-most LED on your OBi, indicating that it is ringing, but no ringy-dingy sound comes out of your telephone, and, when you pick up the handset, voila, the call can be answered, and audio works both ways?
OR, did you mean something else?