Welcome to the world of mobile phone pricing.

AT&T's not coming straight out and saying why, but it is refusing to let some customers with the original iPhone get the iPhone 3G S at the upgrade prices.

What really rankles is that last year, all iPhone owners were allowed to upgrade to the iPhone 3G at the subsidized prices because they had paid full price for the first-generation (that model had not been subsidized by AT&T). Now, however, people who didn't make that move last year are not offered the same deal.

That disparity has really pissed off some people. "So let me get this straight, my line shows eligible for upgrade on 8/11/2009 (18 months), but because I am not upgrading from an iPhone 3G, I have to wait until then even though someone who got an iPhone about 12-13 months ago can?" asked an AT&T customer identified as "" on the company's support forum. "We have a Family plan and spend over $300 a month with AT&T, but if I have to wait 18 months and someone who got a subsidized iPhone a year ago doesn't, I am bolting to another carrier."