That's kind of fucking ridiculous...I would just tell them your story. Tell them that you paid for over $100-worth of shit already, and you would assume that they'd be like, "Okay. Yeah, sure. Makes sense." Well, you would think. You pay with a credit card I assume? I would think that would make it even more clear that it was a mistake. Don't know what else there would be to do...I mean, I think the fact that you paid for a ton of stuff already would make it look far, far more plausible that it was an accident.
~D-Draw
Out of curiosity, how did they get you anyways?