Please help me I'm being sued by a collection agency?

Yesterday of all days I received a note that I was being summoned to court for a credit card that I had 5 years ago. They are saying I owe them 2,400 plus interest however the card they gave me was only 300.00. I learned my lesson and have been trying to build my credit and now this happens. What do I need to do? I'm looking for a job right now and am on very low income with my husband. We can't afford to settle for the 2,400 and I dont believe we should have to pay that much when it was only 300.00. What do I need to do and what will happen if I don't show up for at court? Are there any pro bono attorneys that might take my case? I am desperate and I know that credit card companys are very mean especially with the interest rate thing. If they charged off the account are they allowed to add interest?