WOW.
It wasn't like he went a few over and you could say it was an accident. 4900 over on purpose...that's serious. I think whatever minimum wage is in your state (lets say $5 hourly for easy math but I know it is more), he should have to do housework as many hours as it would take him to pay the bill if he had another job. So that would be 100 hours of housework at $5 hourly to pay you back the $500. I mean, I guess you could cut that in half and be nice but I would be mad. I don't think 14 year olds need cell phones anyway unless it is for emergencies, so he is very privileged.