We have an ancient Norstar phone system, and one of our users has a button on her phone that's programmed to pick up her boss' line. Well, she's moved to a different department and doesn't want that button on her phone anymore. If I go into system programming under Terminals & Sets > Her Extension > User Preferences > Button Programming > Button 21, I can see that it's currently defined as "ANSWER 6291", but don't see any way to clear it. How can I remove the answer feature from this button?