It is a time barred debt as the SOL in New Jersey is 6 years. Is it small claims court they are suing you in? I suggest calling the court house and ask them if it is indeed a real court case by providing them with the docket number. Some of these Junk Debt Buyers will use fake court papers to get you to pay. It is illegal if they do.
If they called you after 9:00 pm that can be up to a $1,000 violation and you can sue them in court. Depending on your states Civil Rules Of Procedure, You may be entitled to treble damages. DO NOT talk to the debt collector on the phone, they will try to trick you. If they did in fact file a false court document, hold on to it as that is also breaking the law.
Call the court house first though and ask them what you need to do to respond. It may help to note to them it is time barred if it is in fact over 6 years old.