mknops,
Well, in this case, you have to separate the logic out a bit and consider the voice processor and the phone system to be separate entities; which they are.
So to change what a phone goes to when it dials 0 is separate from what the Voice Processor has programmed for its dial 0.
Go to System > Device and Feature Codes > Phones > {local} > {extension} > Associated Extensions > Attendant: Put in where you want dial 0 to go.
There is also a Primary and Local Attendants that come into play as well, but for what you were asking for this is the answer.
Thanks,
TE