This is how it should be done.
#1 DV only a CA
#2 The OC doesn't have to answer the OC letter UNLESS you have disputed & received an update by the CRA stating *verified*
#3 The CA has to answer the DV within 30 days or stop collections!
It is always better to deal with the OC if you can. They must agree to PFD if they own the account.
What is the DOFD and SOL on this account?