Once you get your report, go through it carefully. If it contains wrong information, you will have to write back asking that the wrong information be removed. You should provide copies of any proof the information is wrong.
You should then write a letter to the company that gave the CRA the information (the furnisher). Let it know the information is wrong, and it should tell the CRA to take the information off your report. Remember, the company probably doesn't know who you are. Do not assume the person who opens your letter will know your account number or what you are talking about. Be very clear in your explanation of what is going on and what you want them to do.
You will then have to wait to see what the CRA and the furnisher will remove from your report. If everything you want removed comes off, then that is all you can do. As I said in the beginning, you have to understand the impact of your actions. You see, under the law, you cannot receive any damages until you have given the CRA an opportunity to fix the mistakes. They have to do a "reasonable investigation". If they do so and take the wrong information off your report, they are not liable for any damages. If you tell them the report is wrong, they don't take it off and then you try to use your credit but are turned down or you get a higher interest rate, then you may have the right to sue the CRA and the furnisher.
Here is another rub. Your request for a reinvestigation has to be to the CRA. When you go to a website for your report, you may actually be going to another company. If you complain to the company and then sue the CRA, the real CRA will say you never gave it the opportunity to fix the report so your lawsuit will get thrown out. Thank Congress and the CRAs for this neat trick.
I hope this helps. Good luck.