I have used it successfully on watches, but never tried it on a phone.
I really think it's not worth the risk, to be honest. The chances are that you'll make the situation a lot worse. Using an abrasive to remove scratches from a highly-polished surface doesn't make much sense. Fair enough on a matte/rough surface, but not glass or plastic!
steel wool on a glass surface with coating on it? Why not just use a sandblaster and finish it off with some furniture polish