you can easily unlock an SK (with T-Mobile's permission, of course). So it�s pretty straight forward: you have to call up T-Mobile customer service and ask them to allow you to unlock your phone. Really, this process should work with any SIM-based T-Mobile phone. Now, if you�ve been a customer for longer than a few months (some internal governing policy probably in place to avoid unlocking recently carrier-subsidized phones), then you give your IMEI (the unique ID code of your phone) and in 24 to 48 hours you�ll get an email that will tell you how to unlock your old SideKick and use it for other things.
Thank you for taking the time to contact T-Mobile. Below you will see the Instructions for unlocking your Sidekick device.
NOTE: If you receive an error message while performing the instructions below, stop. Please be aware that if an excessive amount of incorrect attempts are made, the phone will be permanently locked. Verify the IMEI by pressing *#06# and submit a new request.
1. Insert the foreign SIM card 2. Power the phone on and the display should read �Special Code Required� 3. Enter the unlock code and the phone will reboot and try to reconnect to the network
Please be aware that the Danger Sidekick�s GPRS-data software will only work on the T-Mobile USA network. The Sidekick�s voice and text messaging functions should continue to function correctly with another carriers SIM card after the phone is unlocked.