Negligent services

I had accounts that was pretty dead, for over a decade I checked with Transunion and after investigations they confirmed the account my be prescribed, but I didn't realize those accounts still sitting on Experian, after disputing with them, no investigations, they say last payment was last year, I never had contact with this account for over a decade, they refuse to validate the payment that the creditor claimed they received, how do I escalate this further, can I take legal action against Experian????