When a lender charges off an account, regardless of the reason, they may opt to pursue it through their own collection department, or they may take a payout from an insurance company, or even a tax credit. If they have taken an insurance payoff or a tax credit, then they cannot sell the account to anyone, nor can anyone other than the insurance company that paid the original creditor pursue collection on the account. This is called legal right of subrogation of the debt. I would ask the plaintiff to show that they have legal right of subrogation of the debt.
Filing a motion for dismissal requires a compelling reason. Read my article, and study the many posts on the site, to see what applies to your case. You will find your reasons there.