If a debt collector contacts you about new accounts opened in your name or unauthorized charges made to existing ones, respond immediately in writing—and keep a copy of your letter. Explain why you don't owe the money in question. Enclose copies of any supporting documents, such as an official identity theft police report or an FTC affidavit.
Also ask the debt collector for the name of the business trying to collect the debt, and the amount allegedly owed. Then contact that business—also in writing—and request copies of the credit applications or any other documents linked to transactions you believe were made by the identity thief. Send these letters by registered mail, and get an acceptance receipt from the post office.