If your friend's account has been overdue in the past (or currently for a lengthly amount of time) the video store might have your card information on file with that account. Not only that, but any late charges accrued for anything will automatically go on your card. It's the video store's fault and you'll need to go down there and have your card removed from the file, davinxtk. Even if you've never signed a contract with them. It's always a good idea if possible, to pay cash for those sorts of transactions.
As far as the bank is concerned, I would have to side with pern on this. It matters not how far your account is in the red, unfortunately they will take the charges out unless you go down there and ask that they take them off. I've done that plenty of times until I got overdraft protection. They usually were pretty good about taking the charges back.
Good luck.