I'm surprised that
1) You didn't look at the services/products you were buying to know how much they were going to cost.
2) How a company is willing to let a customer get to $500 negative account balance ('debt'). Could easily be avoided with an authorised payment scheme set up through PP or with your Bank.
But in regards to what you should do, depends on your circumstance. Just been skimming the comments and there is mention of it being someone else's identity/card? If that's true you're an idiot and I hope you get caught. If it's not, ring the company explain the situation and how you were not aware of the costs, maybe they'll cut you a break and help you out. You don't know till you contact them.