When using an iPhone and adding a new contact, the information is automatically stored to the SIM card inserted into the device. However, if you want to add the contacts to a different SIM card, you do need to take a few extra steps to transfer the contact information of your phone and sync it up onto the new SIM card. You may need to do this if your previous SIM card has become damaged and you need to replace it.
Connect your iPhone with the current SIM card to the provided USB cable, and plug the other end of the USB cable into any available USB port on the computer you typically sync your phone with. When iTunes launches, allow it to sync with the iPhone.
Click the "Eject" button next to your iPhone on the side of iTunes. You can now remove the iPhone from the computer.
Unfold a paper clip and insert it into the small hole on the top of the iPhone. Press firmly. A tray will pop out, holding the SIM card.
Remove the SIM card and place in a new card. Close the small SIM compartment.
Reconnect the iPhone to your computer and wait for the phone to sync up. All of your contacts are now placed onto this new SIM card.