Changing the Rules in the Middle of the Game

Just caught Maxed Out on Showtime. Opinions on credit cards and bankruptcy aside, it does seem totally unreasonable to change the interest rate on money someone has already borrowed. it's one thing to say, "hey, you're being risky -- if you want to borrow any more money, we're going to jack up your interest rate."; quite another to reprice your product after a customer has already purchased it.