I reached a settlement agreement, paid it and they closed my account as paid in full, but now they have sent me a 1099 C. Can they do that?

It was very high interest LOC from CashNetUSA which I could no longer afford due to financial problems. I reached a settlement agreement and they agreed to an amount and monthly payments until paid off at which time they would close the account as paid in full but I would not be allowed to use their service again. I paid it off and received the notification of the account being paid in full but now they have filed a 1099 C. I want to know if that is legal and what rights do I have in this?