Make sure that the ccc's are indeed considering this fraud. There needs proof that you authorized him as a user (this is why they record those coversations on the phone), make they show you proof, otherwise, it's still fraud. Admit to no knowledge of his use of the card, this is their way of putting it back on you and sticking the debt back to you.
Once you got the letter stating you were not responsible, was the account closed? Do you have proof in writing that it was closed?

