How to Open the SIM Tray on My iPhoneby Shawn Farner
The GSM version of the iPhone is available in the United States from AT&T Wireless and, unlike Verizon Wireless's CDMA version, contains a SIM card slot. This allows you to swap in a new SIM card should your original SIM card become damaged, or remove your SIM card if you want to give or sell your iPhone to someone else.
Insert your paper clip or pin into the hole next to the SIM card slot. On the original iPhone -- iPhone 3G and iPhone 3GS -- this slot is located at the top of the phone. On the iPhone 4, the SIM card slot is located on the right side.
Push the paper clip or pin down until you see the SIM card tray eject from the iPhone.
Pull the SIM card tray out. This tray differs in size based on the type of iPhone you have. The earlier iPhone models use full-sized SIM cards, so the tray is bigger; the iPhone 4 uses the micro-SIM format, so the SIM card tray is smaller.
Push the SIM card tray back into the phone when finished. You will hear a "click" when the tray is correctly installed back into the device.