Thats theft!

They WILL realise they've made a mistake,sooner or later your going to have to pay and the fact you blatantly knew about it and closed your account thinking you could get away from it certainly wont help you.

Chances are they would have been OK with your situation,mabey smaller payments and freezed the interest ect but now they'll prob demand the full amount owed promptly!

Id go and see them personally...

Did you have insurance on your card?As some companies will clear off your debt upon loosing your Job?