For Seniors: Search for Contacts on iPhone 4S
If you're looking for a particular person's phone number or other contact information in your iPhone 4S, use the Contacts app. With iPhone 4S Contacts open, tap in the Search field at the very top of your contacts list. The onscreen keyboard opens.
Type the first letter of either the first or last name or company; all matching results appear. In the example, pressing N displays American Health Network, Nancy Fletcher, Nolan Lichti, and Nancy Muir in the results, all of which have N as the first letter of the first or last part of the name.
Tap a contact in the results to display that person’s Info page.
You can't search by phone number, website, or address in Contacts at the time of this writing, though you can search by these criteria using Spotlight Search. Hope that Apple adds this functionality in future versions of the app!
You can also use the alphabetical listing to locate a contact. Tap and drag to scroll down the list of contacts on the All Contacts page on the left. You can also tap on any tabbed letter along the left side of the page to scroll quickly to the entries starting with that letter.