Apple and AT&T are together considering carrier-specific changes to the iPhone firmware, anonymous sources claim. A future update, possibly iPhone 3.1, may introduce two particular features designed to support AT&T's network. The first is an overage alert, which would take advantage of push notification to display a badge, message or sound whenever monthly voice minutes are used up.

The option would be enabled through a device's "Phone" preferences menu. Also under the menu could be a new "Voicemail" setting, which would let users disable the custom introductions in front of their inboxes. It might likewise be used to skip other people's introductions, though only if they are AT&T customers.

Apple has generally resisted concentrating on individual carriers, preferring to develop technologies which can be supported on multiple networks, such as Visual Voicemail. The sources suggest however that if the new features are approved and implemented, they may be expanded upon in the future. The update with overage and voicemail adjustments could allegedly arrive before the end of 2009.