Unlike other smartphones such as BlackBerry's and those that run Google Android, Apple's iPhone doesn't allow users to back-up their contacts to the SIM card. Instead you'll need to copy them to phone's memory and then back them up on your PC.
Keep a copy of your contacts just in case you lose your handset
This means that should you be unfortunate enough to lose your smartphone, you'll have a record of all the names and numbers you need. Furthermore, if you get you get a new handset, whether replacing a lost iPhone or upgrading to a new one, you'll be able to simply plug the device into your PC and quickly copy across all of your data. Here's how.
From the Home screen, select Settings.
Select Mail, Contacts, Calendars and then scroll down and press Import SIM contacts. This will copy any phone numbers stored on the SIM to the memory of the iPhone.
Now connect your iPhone to your PC using a USB cable. If iTunes doesn't automatically open, press Start and select the program from the list.
Once iTunes has opened, press the iPhone icon that appears on the left-hand side of the iTunes window.
From the options displayed, click Info And then tick the box next to Sync Address Book and Contacts.
Now press Sync at the bottom of the screen and all your iPhone contacts will be copied to your PC.