Later today AT&T will open up two different upgrade services related to the iPhone 4S, according to an announcement. The first is the AT&T Upgrader App, which will let people both check upgrade eligibility and preorder a phone, although preorders are only scheduled to start on October 7th. The software will be available for existing iPhone owners through the App Store. AT&T subscribers with other devices will have to visit att.com/phoneupgrade.
