There are many reasons why you might need to find out who is behind a phone number you don’t recognize. If someone keeps calling and hanging up when you answer. If you keep getting a call from the same number but they won’t leave a message. Or even worse, if someone is harassing you and won’t leave you alone. If any of these things are happening to you and you cannot figure out who is behind it, you’ve probably thought about using a reverse cell phone directory to find out who is calling.