Contact the collection agency and ask that it verify the debt. The agency's name, address and phone number should be listed on your credit report or provided to you when you call the credit reporting bureau's toll-free number.

The collection agency must give you information about the amount of the debt and the name of the original creditor and inform you that you have 30 days to dispute the debt. If you do not agree that you owe the money, dispute the debt immediately in writing. Send your letter to the collection agency by certified mail with a return receipt requested.

Also, dispute the debt in writing to the credit reporting bureau(s) that list it. (Instructions for disputing information on your credit report should have been sent with the report.) You should also search your records for any proof that you paid the debt, such as canceled checks or a statement showing that the balance was paid. If you find anything that supports your contention, send copies to the collection agency and the credit reporting bureau.