All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
Dealing with credit cards as well as selling the debt to a third party are among the things that the person should enquire about before accepting to do them. Now that this has happened, you must return the money to the collection company as soon as possible if the loan is due. On the other hand, it is unlawful for you to give the equivalent of the loan to charities or others as long as you can transmit the amount due to its owner even after a period. Finally, you should not pay back Riba (interest and/or usury), if any, in this transaction.
Allaah Knows best.