Well, I somehow managed to keep my unlimited while getting the upgrade pricing. See screenshot.
I'm not sure if the steps I did made the difference or if they're systems were buggy at the time or whatnot but I'll post what I did.
I went to upgrade my device, clicked "month-to-month" then selected the note II, titanium grey, yes to new sim, yes to global. Then it asks what plan, I clicked "Individual" then went back to "Keep current plan". When I went to the next screen, it did NOT prompt me to change my data to a tiered plan.
Anyway, maybe I got lucky somehow, or maybe someone else can do the same thing. Either way, good luck!