Consumer Reports says to avoid any problems you should check your credit reports annually. And be sure to get a report from all three reporting agencies. The information isn't always the same. If you see a problem, correct it in writing. Consumer Reports says mistakes aren't necessarily the fault of the reporting agencies.
Wrong information can come from any number of places, including banks or retailers.
But you will need to notify the three agencies to correct it. And be sure to double check to be sure the error is corrected. You could be denied a loan because you have too many accounts, even if you aren't using them.