Admittedly, I don't remember seeing any app for that, much less think that anyone had ever thought of that.
I just use GV for everything and don't see any reason to bounce things around like that. If I want people to hear a different VM answer, I would just record another greeting in GV and switch from there. I haven't touched my verizon mailbox since I got GV.
I hope someone has something more to your liking.
Its on the Mac (or PC) google, com / voice>settings>phones."deactivate google voicemail on this phone"
phew!
fish
ask a question around here, and get
WHY DO YOU WANT TO KNOW THAT??
Inquiring minds NEED to know-THAT'S WHY!