heh funny you asked this i was just wondering this the other day.
The version in the AT&T song is Daydreamin’ by Lupe Fiasco featuring Jill Scott which sampled from I Monster’s version. I Monster heavily sampled from the original Day Dream by Wallace Collection from 1968 but changed the vocalist.
I think Jill Scotts voice sounds amazing but im not a fan of the rapping done by Lupe Fiasco. Someone needs to mix Jill Scott’s into I Monster’s version. ^_^