It is unclear as to whether they are considering the prior letter a DV, or as a dispute under the FCRA.
While the FDCPA does use the term "dispute" with respect to a DV request, it is an entirely different animal than a dispute under the FCRA.
Disputes under the FCRA require identification of a specific inaccuracy in their reporting, and sufficient supporting documentation to enable them to investigate the asserted inaccuracy. A DV requires no supporting documentation of an error, simply a request for verification of the debt.
Their letter, as to legal implication, is a non-entity. If you consider your DV timely, they simply remain under a cease collection bar. Unless and until they conduct efforts to collect on the debt without first providing the requested debt verification, there is no violation of the FDCPA.
I would send a simple letter back to them, making it clear that your prior letter was a DV request under FDCPA 809(b), and not a dispute of credit reporting under the FCRA.
I would send them as much information as is posted to your credit report identifying the debt. If sufficient to get it reported, then it should be more than sufficient for them to identity their own account. If you received dunning notice, look of any account identification on that notice
I would conclude my letter with a reminder that they remain under a cease collection bar as of the date of receipt of your earlier letter.
Failure ot have provided debt verification is not a basis for a dispute of the accuracy of their prior reporting, so I would not take that path.
