Always DV in writing. CMRRR.
Send 'em a letter CMRRR. Use their address listed on your CRs. Do you have the name of the person who spoke with and the phone number you called? Assuming you do, send something like this.
"This is a follow up to my request for validation of this debt that you claim I owe. On <month> <day> of this year, I called your office at <phone> and spoke with <name>. I was told that I would be provided with validation of this debt. To date I have received nothing from your office validating this debt, but it continues to be reported on my credit report in violation of the FDCPA.
I am again requesting validation of this debt. It is beyond the period allowed under the FCRA to be reported to the credit bureaus. Delete it immediately from any and all credit bureau reports."
Feel free to tweak it to your own style of writing. Don't cut and paste in statutes. General references are better, IMHO.
Also, go ahead and dispute with the CRAs as too old to report.