In my OBi200 under Voice Services -> SP1 Service where I am using Google Voice there is an option to enable message waiting. With I turn this option on the phone always says that there is new voicemail when there is not. I would like to use this feature as I previously used it with a different provider on a Linksys PAP2T but I have never been able to get it to work properly on this device / account.
GV no longer implements that MWI signal. Been so for several years.