I'm such a F!*k%$g Idiot. What should I do?

Don't be alarmed. The letter they sent you is a bluff. Trust me I have had worser letters than that.They can even say to you . You will owe them �2000 if you do not show up, It doesn't mean you have to pay and certainly does not hold legal weight. If I was you I will just cancel my card or even if they took money out request it back through your bank as a transaction dispute.