If a debt collector contacts you about a debt you’ve already paid, let them know that you paid the debt by providing confirmation of your payments – but make sure first that you’re confident it’s not a scam.
If you’re sure that you’re talking with a legitimate debt collector, you can send copies of documents that prove you made the payments, including cancelled checks or credit card statements. You may also include copies of any correspondence about settling the debt. Don’t send original documents – only copies – so you can keep the originals as proof.
If you don't have documentation of your payments or letters saying you've paid off the debt, you can contact the creditor who you originally paid to get this information.