Open up your address book and highlight an entry by scrolling on top of it. Press the menu key (the one with all the dots on it to the left of the trackball) and choose "view". From there, press the menu key again and scroll up to the option called "copy to SIM phone book." Click on that and it will copy that one entry to your SIM card. You'll need to repeat those instructions for every contact that you want on your SIM card.

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