I recently experienced the same thing with a company i debt validated. I also contacted the CRAs to inform them that my request were being ignored, in hopes of them deleting a tradeline.
This is what they told me...
This is not their problem and that I needed to file a compliant with the FTC. Their only responsibility is to dispute the account. If they verify they are out of it. They are not obligated to remove tradelines when the CAs don't validate.
Taking their advise I filed a compliant with the FTC. Took me all of 5 minutes.
Within 2 days the account was deleted and I received a letter from the CA stating that they will no longer pursue collection.
File a compliant with the FTC, and if that doesn't work, I one with the BBB an their state attorney general. Don't stop fighting...lots of people do this. If you quit...you lose.
Be blessed...