You should retain an attorney to defend you in this matter. If you do not file an answer to the complaint within 20 days of service, a default will be entered against you. Once the default is entered, you will have to ask the judge to set it aside (which can be difficult to do). In this economy, credit card companies are suing everyone to collect unpaid debt. You may have several affirmative defenses, depending upon the specific facts of your case. The credit card company will have to produce records to prove that this is your debt - if they can't do it, then you may be able to get the case dismissed. If it is outside the statute of limitations, you may be able to get the case dismissed. Many credit card companies wait too long to initiate the lawsuit. As you may have several defenses, you should contact an attorney to represent you immediately - before the 20 days expire.
If you have any questions, please do not hesitate to contact me.