in the complaints to the AGs, BBB and FTC, you state you tried to obtain validation per FDCPA 809 and the CAs have not responded but continued collection activity past the 30 days window.
in the ITS, basically the same, you notify them of violation of the FDCPA 809 and give them one week to stop collection activity - after that date you will consider them in willfull violation, demand $1,000 statutory file per violation, and file suit without further notice.
I think the CA has correctly stated the law. There is not period under the FDCPA for a CA to respond to a DV letter. They must only desist collection activity until such time as they choose to validate.
If you seek action regarding your credit report, the path to take is not a DV letter, but rather a dispute under section 611(a) of the FCRA, provided you dispute all or a portion of the debt.