Watch this video to learn how to remove the back cover of the G1 Android phone and replace your sim card
replacing the sim card of g1 android video
1slide the screen up to reveal the keyboard
2there is a small latch/tab holding the back cover in place. It is to the left of the "Q" key as you look down on the device. Insert your finger nail between this latch and the device and gently pry open.
3Once the tab releases there is nothing else holding the back cover in place except for friction. gently pull the cover off. Turn the phone over, remove the battery and slide the sim card out