SHOW UP!
Getting sued by a debt collector can be very intimidating, even if you don't owe the debt. In fact, getting sued by a debt collector is so intimidating that the majority of time the defendants do not show up to the hearing - which is exactly what the debt collector wants. The unfortunate result of no-showing your hearing is a default judgment for the debt collector, meaning that the judge will treat your failure to respond as acknowledgement of whatever claim the debt collector has made against you. For this reason, unscrupulous debt collectors have made a lucrative habit of suing on debts that have not been substantiated, or suing for more money than is actually owed.
It is almost always in your best interest to respond and make them prove the debt, if they can. A little bit of courage can go a long way. Simply showing up to court often can be enough to get the other side to offer you a settlement before the trial begins.
PLEASE NOTE: All situations are unique and this should not be used in place of legal advice for your issue. Talk to an attorney to find out what your best options are.