What is the Statute of limitations on a civil judgement in t

I Live in NYS. In 1996 a previous landlord sued me and my husband for back rent and damages to an apartment. She won a judgement because we did not go to court, we were out of state. She tried to freeze my bank account but it was empty. We did not hear another thing until now, almost 15 years later. A collection agency is hounding us relentlessly and sent an information subpena that says if I do not answer in 7 days it is contempt of court. The debt wass just over$1000 and is now almost $5000. What can I do?