Many are private companies that want you to sign up for something -- NOT FREE!
If you see a discrepancy, contact the credit bureau. The bureau has 45 days to fix it. If they re-verify the problem, it will still appear on your credit report.
Only one website is authorized to fill orders for the free annual credit report you are entitled to under law — annualcreditreport.com.
Other websites that claim to offer “free credit reports,” “free credit scores,” or even “free credit monitoring” are not part of the legally mandated free annual credit report program.
In some cases, the “free” product comes with strings attached. For example, some sites sign you up for a supposedly “free” service that changes to an account that requires payment after a trial period. If you don’t cancel during the trial period, you may suddenly see that you are being billed for your "free" service.
Some “imposter” sites use terms like “free report” in their names; others have URLs that purposely misspell annualcreditreport.com in the hope that you will mistype the name of the official site. Some of these “imposter” sites direct you to other sites that try to sell you something or collect your personal information.
Never answer an email from a company claiming to help you. Always go to a search engine and enter the information yourself. Again, there are many evil people trying to collect your personal information. So be very, very careful.
If someone calls you on the phone about problems with your credit report, don't give out any information. I had a phone call from "Chase Bank" one night around 9 pm. Something about the person on the phone seemed "funny" to me. I hung up and dialed the 1-800 phone number on the back of my Chase credit card -- they had NOT called me -- it was a scammer trying to scare me into giving them my personal data.