I sent to all 3 CRA. I forgot to include SS#. CSC accepted, TU and EX sent letters back needing identification.
By the time I got the letters back from TU and EX, CSC's 30 days were nearly up, so I waited to see the outcome before spending money on CMRRR to TU and EX again.
CSC deleted 2, but during the 30 days that creditor deleted those two accounts from my EX on their own, so I assume they didn't verify with CSC is why they got deleted. CSC "verified" the Midland and left it, even though I sent the letters, GC, etc to CSC proving Midland was in violation and not responding to disputes.
For me, no success. For others, I have read of success. HappyDays has had success.