Close the accounts that you know or believe have been tampered with and notify the sponsoring institution(s) of the theft. You usually have to provide the company with two documents: 1) a report filed with the local, state or federal law enforcement agency and 2) an identity theft report.
Some companies provide their own forms for the latter, but most accept the Federal Trade Commission's Identity Theft Affidavit, which is available online at www.consumer/gov/idtheft. There, you can also find a link to file your complaint with the FTC. Or you can call the FTC's Identity Theft Hotline at 877-438-4338, or write to:
Identity Theft Clearinghouse, Federal Trade Commission
600 Pennsylvania Avenue NW
Washington, D.C. 20580