this is only thing related i can find but it does not help..
GV Voicemail Notification & Missed Calls
When you enable Google Voice voicemail notification on your OBi, you should be sure to not check the "Place missed calls in the inbox" box. Otherwise, whenever there is a missed call, the phone attached to the OBi will signal (visual and stutter dial tone) an unheard voicemail. The Missed Calls setting can be found in the Google Voice Settings: Calls tab.
can anyone tell me if its even possible to get notification on phone of missed call and voicemail?