If the CA put the collection on your credit report she is correct. Only the CA can remove it. But......
What you can do is offer to PFD the OC IF the OC still owns the account, and have the OC instruct the CA to delete the baddie from your CR.
I was successful in having 3 med collections deleted using this tactic.
Be SURE to negotiate a duplicate original on hospital/dr. letterhead of the OC instructing CA to delete the account from your file.
Hope that helps.