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?
Getting notifications of voicemail is part of the default setup. It's indicated by the stutter tone and a visual indicator if your phone is so equipped. Missed calls for me is provided by my phone, when it doesn't answer a call the display indicates a missed call.
Assuming your OBi is setup with your phone (you can make, and receive calls), the fault MAY lie with your VoIP provider, at least for the voicemail indicator. If it's GV (you didn't indicate), then it should work following the setup instructions.
Leave yourself a voicemail and see what the indicator does.