To unlock the Sony ericsson W20 You can use the unlock code,You can get the unlock code and instructions from here
Theunlockspot.com and Unlock it from Network lock,You can enter the code using the instructions below:
Sony Ericsson W20 Unlocking Instructions
Warning : Do not enter any wrong unlock codes on your Sony Ericsson W20 mobile phones. If you enter over a certain amount of wrong unlock codes on your Sony Ericsson W20 mobile phone, your phone may get hard locked and sometimes become unusable.
1 - Switch ON your Sony Ericsson W20
without any SIM Card,
2 - Press the
left arrow key/button
once,
3 - Press the
button * twice,
4 - Press the
left arrow key/button
once,
5 - The message "Personalize with MNC2" will appear, (or you will have displayed an unlock menu, select the lock you want to unlock)
6 - Enter the Unlock Code.