New York - Sony BMG's (NYSE: SNE) RCA Music Group announced on Monday that Alicia Keys' "No One" has become the first ringback tone to be certified "Gold," representing sales of over 500,000 copies. A ringback tone plays when a caller dials your cell phone number -- instead of the usual ringing. RCA added that the song has also sold over 2 million master recording ringtones, and that Keys has sold over 4.3 million mobile downloads since the end of last year.