Model : Treo 180 & 270

1 - Switch ON your phone without SIM Card,
2 - Type : *#*#CODE#

Model : Treo 600

1 - Switch ON your phone with Allowed SIM Card,
2 - Go to Menu and select "Phone Tool" or "Phone Application"
3 - Type on Virtual Keyboard *#*#CODE#
4 - Select with stylus "Number" and phone will show that it's unlocked.

or

1 - Switch ON your phone with a disallowed SIM Card,
2 - Enter the Unlock Code we send to you.

Model : Treo 650

1 - Remove Treo battery, unplug cable
2 - Insert incorrect SIM card (one the phone does not accept)
3 - Power on Treo-650, “SIM NOT ALLOWED” is displayed, click “OK”
4 - Go to the dial pad, and use the stylus to enter the unlock code, then press “Dial”
5 - Phone will reset and display “SIM LOCK REMOVED”

If the above method does not work enter the code like this *#*#CODE# dial

Model: Treo 750

1 - Remove Treo battery
2 - Insert incorrect SIM card (one the phone does not accept)
3 - Replace the battery and the cover, Windows may boot automatically.
4 - Turn the phone on if it does not start up when the battery is inserted.
5 - The phone will ask for the unlock code.
6 - Enter the unlock code provided using your stylus then tap "OK"
7 - Your Palm Treo 750 is now unlocked..

 - If you see a message that says "Timeout" just leave the phone on with that screen and the message will disappear after a while and prompt you for the unlock code again
 

Troubleshooting:

Error Message:  "The SIM Lock has NOT been removed from this phone"

        Solution 1: Please make sure you are entering the correct code and enter it using this method *#*#CODE# dial

        Solution 2: If the phone says that the SIM lock has not been removed, ensure that the phone radio is on.