Go to walmart, by this stuff called Scratch-Out in the automotive section. I used it on BMW's and just about anything and everything that can scratch and it does work!
http://www.kitwax.com/html/kitProducts.htm
I admit never using it on a phone, but just about everything else with no visible remains of a scratch...
If it doesn't work on your phone, if you have a car you didn't waste your money!