As you probably know, using the iPhone means choosing AT&T Wireless as your cellphone carrier. If you're a Verizon, Sprint, or T-Mobile fan, too bad. AT&T (formerly Cingular) has the iPhone exclusively at least until 2012.
Why did Apple choose AT&T? For two reasons.
First, because Apple wanted a GSM carrier (SIM Card Slot). Second, because of the way the cellphone world traditionally designs phones. It's the carrier, not the cellphone maker, that wears the pants, makes all the decisions, and wields veto power over any feature. That's why so much traditional cellphone software is so alike—and so terrible.
On this particular phone, however, Apple intended to make its own decisions, and so it required carte-blanche freedom to maneuver. AT&T agreed to let Apple do whatever it liked—without even knowing what the machine was going to be! AT&T was even willing to rework its voicemail system to accommodate Apple's Visual Voicemail idea (Visual Voicemail).
In fact, to keep the iPhone under Apple's cloak of invisibility, AT&T engineering teams each received only a piece of it so that nobody knew what it all added up to. Apple even supplied AT&T with a bogus user interface to fake them out!
Suppose you've already activated your phone (Appendix A), and the "number of bars" logo in the upper-left corner tells you that you've got cellular reception. You're ready to start a conversation.
Well, almost ready. The iPhone offers four ways to dial, but all of them require ...