Need to first try to find out if someone close to you are responsible for it. (ID thleft is very common, usually a friend or family member)However, you need to prove to the credit breau it wasnt you; you can mail them the information: proof of residential address at the time of the account, police report, copies of SSN card, birth card, state id, type a professional letter stating the issuse at hand. And they will reply via postal mail telling you what to do next or with a letter telling you that they have deleted or updated the account you disputed.
Currently go through this...........I am a jr so my father screwed his credit and began using my SSN when I was 15 years old.