Are you hearing things? The music accompanying the spot for AT&T's Personal Network sounds so suspiciously like Madonna's ''Ray of Light'' that a lawsuit may seem inevitable. Well, hold on to your litigation: The music really is ''Ray of Light,'' and the Material Girl actually gave the corporate giant permission to use her material. ''We thought [getting the song] was a long shot,'' says Ted Littleford, executive creative director of Foote, Cone & Belding New York, which came up with the spot. ''It was a great coup.'' Littleford won't say how much AT&T paid to express itself, but you can bet it was considerably more than your last phone bill. For her part, Madonna, who is hardly accustomed to licensing her songs for commercial use (let alone one still in heavy rotation), is comfortable with having the tune double as a jingle. ''The song is about communication and modern technology,'' she says, ''so I think it's the perfect combination.'' Note to Mrs. Paul's: ''Frozen'' is ready and waiting.