His unlimited data. From my experience with VZW, nothing is easy with their system, so I wouldn't be surprised if they would have to place another order, rather than just take $50 off.
If you aren't saving an unlimited plan, then I'd go right ahead and do it.
My GS3 is on order. I just got a post card today with a $50 discount for my line. I'm trying to decide if I dare call and ask them to apply it to my order and risk messing up the order somehow. Or maybe I'm just being paranoid. What do you think?