I went through the same thing w/Citibank. Your debt settlement company should have a litigation dept that can help you deal with this situation.
You need to reply to the summons within the appropriate time frame. You can get some reasonably priced advice at legaladviceline.com if your DSC can’t help you. Citibank really doesn’t like to deal with DSC or settle debts for less than you owe them.
I was ultimately able to reach an agreement re: a payment plan that I could afford but only after I left the settlement company. The court still found in their favor but I did not actually have to show up in court and did everything by certified letters and phone calls w/the Citibank attorney (I rep’d myself w/help from Legal Advice Line). Hope that helps a bit and good luck!