This happened to us last year and they literally had the wrong person. They started calling my wife at work. I googled their corporate headquarters address and sent them a certified cease and desist letter and we haven't heard from them since. Just google whatever kind of letter you need and you can easily find one to use as a template. Then you can send it certified mail without even having to go to the post office. I used these people and it worked like a charm. Totally worth the 8 bucks it cost me. I even got an email when someone signed for the letter. https://www.onlinecertifiedmail.com
*DELETE* I read the OP more carefully and he's already checked the credit reports. carry on. And whew.
Statue of limitations is your friend. If I was you, I wouldn't worry too much about it. Just make sure that you go to court. I was sued once like this but I knew that they didn't have the statues of limitations on their side so I went to court on the day that it was supposed to be and and foumd out the company cancelled the court date. If you have your statutes of limitations on your side you can actually sue them. Which is what I would look into like a countersuit.
If they have filed a complaint, I would file an answer, either a general denial, or a denial of each portion of the complaint that is not true, depending on the requirements of your jurisdiction. You don't want to ignore it, because that is how you get a default judgment levied against you. If it is a scam, once you file your denial they will just drop the case (knowing they can't prove anything). I wouldn't waste money on a lawyer unless and until they start requesting depositions.
Good point. I’d recommend the defendant show up already nude to counter his forthcoming counter suit.