The best recommendation I can give, and I am asked this question a lot, is to visit the Federal Trade Commission's ("FTC's") website: http://www.ftc.gov/bcp/edu/microsites/idtheft/consumers/defend.html.
There you can learn the exact steps you should take. Take them immediately, as every day can compound the damage that can be done to your father-in-law's wallet and credit.
After taking these steps, and your problems persist, contact a consumer protection attorney. You can find one in your area by visiting the cite of the National Association of Consumer Advocates ("NACA"): www.naca.net.
Hope this helps. Good luck!
The above is for informational purposes only and does not establish an attorney-client relationship.
Mr. Milz has provided good advice. We also have information at our website. http://www.armstrongattorneys.com/credit-reporting-disputes/
You should be able to find an attorney in the Houston area to assist you, but if you cannot find one you like, feel free to contact our office.
I am licensed only in Texas. Offering information of a general nature in response to a question is not intended to be legal advice in your state.