If you get the call say bye and if you hit the receiver button several time it will clear the line.
I've done this woth those voice message calls about winning a holiday.
Better still leave answer and leave the phone off the hook and play dodgy sounds down the phone (puking, on the loo, or sexy sounds)
Or if you have been to disney a looped payback of "It's a small world", if anything it will drive them mad
