AT&T-Specific Overage and Voice-Mail iPhone Updates on the Horizon?
Apple and AT&T could be planning updates for US iPhone owners in the future, including push-notificiation powered overage alerts, to let users know when they're close to depleting their anytime minutes, and voicemail settings to disable custom and AT&T preset greetings for both your iPhone and for calling other AT&T customers.
AppleInsider, quoting "those claiming knowledge of the matter" (TCKOTM), says:
The proposals are said to be a collaborative effort between AT&T and Apple based off customer feedback. In addition to boosting customer satisfaction with both the iPhone and AT&T's wireless network, the additions could also serve as a steppingstone for additional carrier-specific features, those claiming knowledge of the situation say.