One of the useful features on the iPhone is the ability to quickly look up recently used numbers for redialing purposes. If you primarily use your iPhone to call a few select business associates, this feature can come in very handy as it provides the full list of recent calls made to and from your iPhone. The process for looking up a number to redial is the same on all iPhone models and software versions.
Unlock your iPhone and tap the green "Phone" button on the bottom menu bar.
Touch the "Recents" button to view the list of recent calls or touch the "Keypad" button to redial the most recent call. From the Keypad menu touch "Call" and then press "Call" one more time to redial.
Swipe the screen up and/or down the Recents menu to scroll through the list of recent calls. Tap the number you'd like to redial and touch the "Call" button to redial.