I just got an IPhone recently and set it to use Youmail. Youmail is a great service, but right now I actually found I wanted to just use the visual voicemail that comes with the IPhone. When traveling, I think I’ll want to be able to activate Youmail again because it is very handy the way it send you emails with your voicemails in them – it even transcribes them!
Anyway, I had a hell of a time finding the dialing codes to deactivate Youmail, so I put them here. I put them as contacts in my phone for future reference.
I previously posted a link to this article as having the codes I needed to deactivate Youmail:
http://arstechnica.com/journals/apple.ars/2008/08/16/on-disabling-voicemail-on-the-iphone
It turns out the codes only seemed to work. I ended up having to cancel my Youmail account and they then gave me the codes. Very frustrating.
To disable the Youmail service and revert to Visual Voicemail the code is ##004#. (This is on AT&T or Cingular).