A paid collection is a little tougher to have removed since basically you have no bargaining power..........but it's not impossible. You will just have to be persistent. There are a few things you can try.
You can keep disputing it for various reasons. Just try to dispute it differently each time in hopes that you don't get the "previously investigated" or "frivolous" response.
You can also try going directly to the CA. A DV would be one way to do it (or even a 1 2 punch if you wanted to) OR you could just call them up. Ask them why they haven't removed it from your CR yet (because that was the understanding you had........right?
). Talk to several people if you have to (try to write down/remember names) and call them daily......or more often if you want to and have the time. Stay nice and polite........but be a constant PITA. (Think Columbo......lol always super nice but very annoying with all of his questions
) At this point.......since it's been paid........you have nothing to lose and they have nothing to gain. Their time is money.... and if you waste enough of their time, you may get on their nerves enough to where they want to delete it just to get rid of you.
The latter strategy....is, of course, my personal fav. :D