I did a few times as a teenager, especially when AOL came out and used up minutes! I think when it first came out, I rang up a bill over $1K!! My parents were FUUUURIOUS (putting it mildly).. Also, Sr year, I got a boyfriend and who lived in a different area code, but still within the Chicago suburbs. I didn't realize different area code = expensive phone call. I managed to call the phone company and change our phone plan, and they reversed those charges on that particular incident. PHEW.