False statements or representation: Debt collection

I had a credit card in collections for the amount of $10000.00 and they agreed to settle for $4800.00. I received a check from the finance company ( refinanced the house ) for the full original amount. I sent both check and settlement letter to USAA for payment. They kept the entire $10000.00 and stated, since the check is for the original amount, then the difference will no be refunded