When we were re-doing Little Raven's room, mean and cruel parents that we are, we removed the phone jack, and pushed the wire into the wall, then papered over it. She is only ten now, and really, doesn't need a phone in her room.
As we're doing this, she was in in her room with us, and we were trying to be as discreet as possible. However:
LR: "Daddy, I'm not sure if you noticed..."
Daddy "Noticed what?"
LR "Well, when you put the magnetic paint on the walls, the magnets work right on the wallpaper too!!"
Daddy: "yeah I know, I put it there so that it would do that!" (quickly finishing covering the old phone jack).
It's funny what they'll notice.