To get Your Sony Ericsson W518A model Phone Unlocked,You can use the Unlock code,You can get the Unlock code at hereUnlocking4u
and get the FREE Unlocking instructions here Mobileunlockguide
and Unlocking step by step...You can follow the free instruction below i got it from there Only(mobileunlockguide)
W518a Unlocking InstructionsWarning: Do not enter any wrong unlock unlock
codes on your Sony Ericsson W518a mobile phones. If you enter over a
certain amount of wrong unlock codes on your mobile phone, your phone
may get hard locked and sometimes become unusable.
1 - Switch ON your Sony Ericsson W518a without
any SIM Card,
2 - Press the left arrow
3 - Press the button * twice
4 - Press the left arrow
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.