I had the same problem - this is a typical AT&T bait & switch. I bought the last two iPhones on day 1 and activated them the same day, choosing the highest tier of service they offered. My monthly bill is $120, so that would seem to meet the "your monthly plan must be $100 or more" rule.
Presumably I couldn't be more qualified, right?
No, apparently. According to AT&T, I'm not qualified for the upgrade price until December. My monthly charge is $95 a month, plus $25 in TAX, meaning that I don't qualify because even though I took the most expensive plan they offered, that $5 less a month I've been paying for the last two years is *just* shy enough for them to deny me (& you, I assume) the upgrade pricing.
Admittedly, I didn't read the no doubt VERY FINE print, so certainly some of the blame falls on me (not that I've seen this fine print anywhere yet).
I am still annoyed, especially after waiting in line and then having no Apple associate who could tell me why I was coming up short. I was going to order it online, but when I started the process before AT&T revised the plan, I saw the $700 price tag and bailed on completing the order.
All in all, another badly orchestrated and executed "plan" by AT&T.