Lawsuit from Ozark Capital Corporation

I received a letter telling me that I am being sued by this collection agency over a credit card debt. I live in Texas and I opened this account in 1998 or 1999. The credit card issuer is Citibank and they didn't want to work with me when I tried in good faith to send them a payment for a past due account. They wanted everything to be paid in full. Well, so many years passed and I have not heard one word from them until I was served with a citation on April 14th. I filed my answer already this past Monday. I received some assistance from this legal center and got an answer typed out for me basically denying the debt. I also sent the attorney Melvin Thathiah who works for Hosto and Buchan requesting validation of debt. I sent it certified as well on the 18th of April. I am wondering what is the next step? They have 30 days to validate the debt right? What hppens if they can't validate it? I requested original application with signatures, statements, last activity, etc. They also lied on my affidavit saying that they heard from me on May 12, 2005 but that is a lie because I have not been in touch with them since 2001. I know for a fact that I didn't get in touch with them because my dad was in the hospital around May 12th of 2005 and I was with my family celebrating his birthday. Is there anything else that needs to be done I am pretty worried. I don't want to go to court. Thanks!