Galaxy S3 buyers that are looking for an easy way to unlock their smartphones will be happy to hear that there’s an application available from Google Play ready to help with that. Unfortunately it’s not just good news for you, as the app will only work on GT-I9300 Galaxy S3 versions and requires the device to be rooted in order for the unlock to work.
The Voodoo Galaxy S III SIM Unlock is the name of the app available in Google Play as a free download, and it’s basically an implementation of Galaxy S3 SIM unlock methods described on the xda-developers forums. The application is still in beta version, so it's safe to assume that it will be improved in time.
Once you run it on a rooted Galaxy S3 smartphone, the app will automatically unlock the handset and you’ll be able to immediately use it with SIM cards from other GSM carriers.
While we’re keeping you updated on rooting and unlocking all sort of devices, we are not advising you to root and/or unlock the Galaxy S3, or any other smartphone or tablet, no matter how easy the process is. In case you’re interested in pursuing such endeavors, make sure you back up your personal data beforehand and follow all the available instructions for such procedures.
Also worth mentioning is that if you paid full retail price for the device, your Galaxy S3 is probably already unlocked, so better test SIMs from different mobile operators before rooting and unlocking the handset.