There are statute of limitaions for collecting on debts that start to run after last payment is made. If you believe that they are not able to collect you could advise them of that and see what they say.
If the case is still ongoing, dispute the debt. Make them prove that they can still collect. If this is a debt collector, dispute that they have the right to collect from you. If you win, contact local counsel for a possible suit against them.
Mr. Goldstein is a Virginia-licensed attorney only. The information is not, nor is it intended to be, legal advice. You should consult an attorney for individual advice regarding your own situation. Answering this question does not in any way constitute legal representation. Contacting Mitchell Goldstein or the Goldstein Law Group does not constitute legal representation, nor is any information you provide protected by attorney-client privilege until otherwise advised.