From the FTC website
Under the FCRA, both the consumer reporting company and the information provider (that is, the person, company, or organization that provides information about you to a consumer reporting company) are responsible for correcting inaccurate or incomplete information in your report. To take advantage of all your rights under this law, contact the consumer reporting company and the information provider.
Tell the consumer reporting company, in writing, what information you think is inaccurate. Include copies (NOT originals) of documents that support your position. In addition to providing your complete name and address, your letter should clearly identify each item in your report you dispute, state the facts and explain why you dispute the information, and request that it be removed or corrected. You may want to enclose a copy of your report with the items in question circled. Your letter may look something like the one on page 4. Send your letter by certified mail, return receipt requested, so you can document what the consumer reporting company received. Keep copies of your dispute letter and enclosures.
Consumer reporting companies must investigate the items in questionusually within 30 daysunless they consider your dispute frivolous. They also must forward all the relevant data you provide about the inaccuracy to the organization that provided the information. After the information provider receives notice of a dispute from the consumer reporting company, it must investigate, review the relevant information, and report the results back to the consumer reporting company. If the information provider finds the disputed information is inaccurate, it must notify all three nationwide consumer reporting companies so they can correct the information in your file.
When the investigation is complete, the consumer reporting company must give you the results in writing and a free copy of your report if the dispute results in a change. This free report does not count as your annual free report. If an item is changed or deleted, the consumer reporting company cannot put the disputed information back in your file unless the information provider verifies that it is accurate and complete. The consumer reporting company also must send you written notice that includes the name, address, and phone number of the information provider.
If you ask, the consumer reporting company must send notices of any corrections to anyone who received your report in the past six months. You can have a corrected copy of your report sent to anyone who received a copy during the past two years for employment purposes.
If an investigation doesnt resolve your dispute with the consumer reporting company, you can ask that a statement of the dispute be included in your file and in future reports. You also can ask the consumer reporting company to provide your statement to anyone who received a copy of your report in the recent past. You can expect to pay a fee for this service.
Tell the creditor or other information provider, in writing, that you dispute an item. Be sure to include copies (NOT originals) of documents that support your position. Many providers specify an address for disputes. If the provider reports the item to a consumer reporting company, it must include a notice of your dispute. And if you are correctthat is, if the information is found to be inaccuratethe information provider may not report it again.