Zombie debt, much like zombies, is tough to STOP!
In walking dead terms, this type of debt is an old account that has "come back to haunt" the debtor when third-party debt buyers purchase the debt from another debt collection agency or debt buyer.
Zombie debt has been previously settled out or paid, or have expired due to a statute of limitations.
Again, Once the statute of limitations is past, collectors can only try to call to collect from the debtor unless the debtor lives in a time-barred State. "They can no longer sue or credit report."