best buy reps generally have very little information about any given topic. they know just enough to sway you to purchase a phone. when they're wrong they pass the buck. tread lightly friend.
i'm pretty sure the didn't offer a similar thing for an older model (the s5 or 6 maybe)? so i won't be surprised if they don't participate in this one either.
edit: the s6 and s6 edge had the promotion, but at&t and verizon did not participate. they also didn't participate in a similar deal samsung offered for dropbox a while back. i wouldn't count on the 100 gigs of free storage.
as far as pay goes, droid life is reporting that verizon told them they were still evaluating it. i would guess that eventually verizon will get on board with samsung pay, but not the free storage. just a guess though about samsung pay though.