To unlock the Sidekick 3 from T-Mobile Network lock,you can use the Unlock code,You can get the Unlock code from hereUnlocking4u
and get the free unlocking instructions below and Unlock it step by step...
Sidekick 3 Unlocking Instructions
Do not enter any wrong unlock
codes on your Sidekick 3 mobile phones. If you enter over a certain
amount of wrong unlock codes on your Sidekick 3 mobile phone, your phone
may get hard locked and sometimes become unusable.
1. Switch ON your Sidekick 3 with a Not ACCEPTED
2. If your Sidekick 3 asks for a PIN code, then enter your SIM card PIN and press OK.
3. Sidekick 3 will ask to enter an "unlock code".
4. Enter Unlock Code we send to you.
5. Your Sidekick 3 is now unlocked.