OK the first question is whether or not it is a valid debt. The creditor does not respond in writing nor do they verify, its the same across all bureaus, if the creditor says 'yes' it says.
You can contact the FTC and I have done so on several occasion with reaged accounts and invalid debts (among other things) and they have been successfully removed. that is your next lne of defense.
If the debt is truly invalid, you can file a complaint against the party online at
www.ftc.gov