Yes, you are sending the DV letter to the CA CMRRR.
There are some sample letters here:
Validation Letters
My favorite is just a very short, simple one (I don't think it's posted here)...
Dear CA,
I dispute your claims in their entirety and request validation pursuant to the FDCPA.
Please note that it is inconvenient for me to receive calls at my place of residence. All future communications with me MUST be done in writing and sent to the address noted in this letter.
Sincerely,
*your name*