Can a debt collection agency sue me using the Original Creditor's Name as the Plaintiff?

I was summoned Sept. 26 (Saturday) and have 30 calendar days to answer. No doubt I am going to file an answer with the courts. The question is....on the summons, the plaintiff is: "Company A " (I'll just call it that for now) when in fact on my credit report it says its a charge-off. The debt collection agency is the attorney representing "Company A" and the atty's name an BAR# is on the summons. The summons is legit as I verified it with the local courts. So, question #1...Why is "Company A" still listed as the Plaintiff? Question #2 - Can "Company A" really still be the plaintiff? or is the underlying "real party" is the debt collection agency? I'm filling out an Answer - Contract form but I'm confused with what to put on the form. First off, I want to deny the allegations that I owe the debt to the debt collecting agency because there is no agreement or contract. Can I do that? But I did have a debt with "Company A" which is stated as the Plaintiff on the summons...what can I say on the summons that would help me in my defense?