Obtain the unlock code for your K800i if the phone is locked. You can
get the code from an unlocking service, or from the carrier that originally
sold the phone.
Turn off the K800i and turn the phone over.
Remove the battery cover by sliding it toward the bottom of the phone.
Lift the battery from the bottom and set the battery cover and battery aside.
Remove the old SIM card by sliding it out from under the metal clip. If
you have an unlocked K800i, all you need to do is insert the SIM card from your
new carrier. Otherwise, leave the SIM out and reinstall the battery and battery
Turn the phone on and wait for it to boot up.
Press left on the navigation pad and press "*" twice, then
press the left arrow again. The phone will display "Personalize with
Type the unlock code and wait for the phone to reboot.
Turn the phone off and insert the new SIM card.
Usually answered in minutes!