Ohh Ohh, I do, I do.
But saying "Vodavi" is similar to saying "Ford" - both manufacturers made a lot of products over their history and you cannot even begin to provide guidance without more information on specific model. That said, many of the Vodavi products required a particular software application in order to make this type of change. Without that app, you're really out of luck. Other products used monitor/keyboard or communications package to access admin terminal. This is something that an on site tech with the right "tools" could fix up in 30 minutes or less. Or you may be able to find the manual on line and widdle thru it if you have the aptitude.