How do you report a credit card that you never knew about?

I had a 3 cases like this. Someone actually had 3 credit accounts opened in my name. How i found out about it was when i applied for a loan and the officer mentioned paying off credit cards. I knew i only had 2..but 3 more popped up. I asked to see the report got the name and acct. number so i could call and report the problem to the companies fraud dept. And everything else happened from there. So first i would say get the acct. information if you can at least he company name if not the acct. number that would work. That way you know who to call and they can pull any accounts that have you social security number listed on the system and the customer service dept can transfer you to the fraud dept. and let them handle it from there. Also that account will be removed from you credit report. Just make sure you tell them.