It sounds to me like their current trick d'jour of "misinterpreting" a DV as a dispute, and asking for more information in order to investigate your "dispute."
A DV, unlike a dispute, requires no documentation of any inaccuracy, just a request that they verify the accuracy of the asserted debt.
So, providing your DV was timely, they remain under a cease collection bar.
You might send them a letter, simply informing them that your letter was a DV, not a dispute, and thus their is no requirement for any additional supporting documentation.
That will put them on notice that they are still under a cease collection bar, and that you have NO pending dispute upon which to request additional information.
