To quote Winnie the Pooh: "Oh, bother".
Well, you could go with the bridged appearence route so the calls are "not" coming from the bigwig's station(s). Or you can give the bigwigs a unique COR so that only certain individuals could call them directly, and everyone else gets a wave-off. Their extension would still show up, but it wouldn't be available to be used by the masses.
Susan
Under certain circumstances, profanity provides a relief denied even to prayer. - Mark Twain