I need someone to tell me what I should do next

In February of 2009 I discovered that the 4 PDLs I still was paying were all illegal. I followed the steps on this forum (Thank you, thank you, thank you for this forum). I closed the bank account, I wrote the letters to each illegal company. I contacted the people I should contact. I did get on paid in full from one company. I got a few nasty phone calls from a couple of the companies. This one company I never heard anything from. Until Friday. ACA Recovery Inc. called at work. They told me they would see me in court. I did get a letter from ACA Recovery on Saturday. The company I had the loan with was Aero Advance. The loan was for $300.00. I have paid them back over $900.00 on that loan! ACA Recovery wants $240.00. I know I should send ACA a letter disputing the debt. The sample validation letters I looked at did not mention the fact that the loan company I supposedly owe does not have a lisence to practice business in my state. (Mississippi). Should I mention this in the dispute letter. Please help. I do not intend to pay aero advance or the ACA collection agnecy.