When a Stranger Calls (2006)

Whatever You Do, Don't Answer The Phone.

Far away from the site of a gruesome murder, a teenager named Jill Johnson arrives at a luxurious home for a baby-sitting job. With the children fast asleep, she settles in for what she expects to be an ordinary evening. Soon, the ringing of a phone and the frightening words of a sadistic caller turn Jill's routine experience into a night of terror.