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CAs are bad, paid or unpaid, and both count equally to the demise of your score. Some here have had success in sending a DV letter to a paid CA. You can search around for some examples. You may need to modify a bit due to the $0 balance. Another option is to dispute. If there is something reporting on your CR relating to the CA, like dates, acct info, etc., then you could do that. Disputing could lead them to delete. Whichever way, they don't have to delete.
Score-wise: I had a 7 yr CA delete last week for at least 18 points. Some have hit 50 points plus. All depends on age of the CA.