Subscriber Identity Module (SIM) cards are small cards that are inserted into mobile phones; they store information about the mobile network of the subscriber. In addition to allowing a cell phone to identify a mobile network, SIM cards also store other small amounts of data, such as contact names and phone numbers. Certain data (media files and phone applications) cannot be stored on SIM cards, however. If you have a new iPhone, the iPhone supports importing contact data from an old cell phone's SIM card.
Power off your iPhone. Hold down the "Power" button in the top right corner of the iPhone until the "Slide to power off" message appears. Slide your finger across this message to shut off the phone.
Open the SIM card holder by inserting a pin or paper clip into the SIM card release valve. This is located immediately to the right of headphone jack.
Insert the SIM card from your old cell phone and put the SIM card holder back into place.
Power on your iPhone by holding down the "Power" button until the Apple logo appears.
Tap the "Settings" icon on the home page of your iPhone. This opens the "Settings" menu.
Tap "Mail, Contacts, Calendars." Scroll down to the bottom of the screen and tap "Import SIM Contacts." A popup message that says "Importing SIM Contacts" will be displayed until the import is complete.