REALLY OLD negative credit listings

I am interested in verifying some old debt that I have ignored- primarily because I don’t believe the debt belongs to me, and because I was young, stupid, and uneducated when it came to my finances. I'm in repair mode now.
Anyway, the item is a medical bill that I’m sure my insurance would have taken care of. I have been doing a lot of research online for verifying/disputing negative credit listings and this is something I really want to move forward with. I want to make sure that I have the correct information though. In reviewing the Fair Debt Collection Practices Act 15 USC 1692g Sec 809(b), it says:
“if the consumer notifies the debt collector in writing within the THIRTY-DAY period described in subsection (a) that the debt, or any portion thereof, is disputed………..etc”.
Well, I am well beyond the thirty days indicated. The listing was originally reported in 2003. Is it too late or can I still request a debt validation letter? If so, who do I send it to? Experian? The collection agency? Or the original creditor?
Help! and Thanks!

The FDCPA only applies to collection agencies.....Experian and the original creditor are not CA's so you cannot DV them.

Who is currently reporting it? If it is the original creditor still reporting, you might wanna talk to them . If your insurance didnt pay it, it is more than likely too late to fix it.

The collection agency is reporting it. I'm almost positive my insurance would have paid the bill. It was for ambulance service.

Is the debt within or out of SOL?