It's bad to keep your phone number from your employer.
Bill, who is suspicious of being spied on, is updating his personal info with his employer and needs to put down his phone number.
Bill wants to finish the update.
Bill gives his real phone number to his employers and reasons that he can avoid them with caller ID.
Bill puts down a fake phone number so his employers can't trace him.
Bill's employers are able to reach Bill at a critical time, helping their business.
Bill's employers attempt to call Bill to come in to work, but cannot find him and are in a bad situation.