Mrs. Minervini,
fdcpa gives you the right to ask for some written documents. Send your request through CMRRR. Once they receive this letter, they must validate the debt, otherwise they cannot start collection activities. If they cannot validate, you need not pay them.
Now, have you contacted the original creditor? It would be of much help if you can show some proof of canceling the contract. Anyway, you have said that you dealt them 6 years ago. Do you know the statute of limitation of your state? If the debt is past SOL, no legal action can be taken against you. Do let us know if you need any more information.