Hello and thank you for contacting us. This is Dwayne B. and I’m an expert here and looking forward to assisting you today. If at any point any of my answers aren’t clear please don’t hesitate to ask for clarification. Also, I can only answer the questions you specifically ask and based on the facts that you give so please be sure that you ask the questions you want to ask and provide all necessary facts.
No, there are capacities in which they can sue other than just owning the debt. As an example, their contract with the lender may require/allow them to act as an agenct of the lender and bring the lawsuit.
What you probably want to do is do discovery and determine in what capacity they are bringing the lawsuit. There are also a couple of inexpensive ebooks that you may find helpful:
Please note, these books are not just collections of forms, they teach you the basics behind the law as well as the concepts. That is much more helpful than just a form.