My cousin got sued for $5,000.00 by a debt collection law firm. It was filed at the superior court. According to the court clerk, superior court handles cases with a claim of over $15,000.00. This current case should have been filed under magistrate court. Am I correct? Should my cousin file a motion to dismiss because of lack of jurisdiction? What should he do?

In my State - NY - the Court will not take a case which is under its limit. Are you certain that with interest and legal fees it isn't over $15,000? If in fact you are correct, file a motion to dismiss.