Usually, even after the debt gets paid, a collection agency contacts because they found the account still unpaid in your credit report or the creditor hired them to collect the money from you. It was the duty of the agency whom you paid the account earlier to update your file with the creditor and the credit bureau. Since they have not contacted and updated your file, you are still forced to pay the same debt which has already been paid by you.
You need to contact them whom you paid this account. Send a formal letter explaining that your credit ratings are being hurt because of their failure to report to your creditors. Thus, they need to do the needful and send you a confirmation letter in writing. The updates done in your credit report will be reflected in the next 30 days.
Explain the same situation to LTD financial services but before you do so, first ask them to validate the account. You first need to know if they are really having your account or just making a blind call. Send a debt validation letter to the company's mailing address through certified mail.