So you want to SIM unlock your beast of phone known as the Galaxy S3? Well we got you covered on that too. In this short tutorial we are going to instruct you on how to SIM unlock your Samsung Galaxy S3, now this only works for the I9300 model. Thanks to XDA developer Spocky12, we have a nice app that can SIM unlock your device quite nicely. Although Spocky12 does tell us that the app may not keep your device unlocked forever, as updates could re-lock your device.
Let’s get started, shall we?
OMG!Droid is not responsible for any damage caused to your device while unlocking the SIM.
This tutorial is for the I9300 Galaxy S3 only, applying this to any other device could result in a bricked device
A rooted Samsung Galaxy S3 GT-I9300, with BusyBox installed (downloadable from the Play Store if it’s not pre-installed).
Enable Unknown Sources on your Galaxy S3 under Settings > Security.
Install a file manager app on your Galaxy S3, such as ES File Explorer, from the Google Play Store.
Download the GalaxSim APK file (GalaxSimUnlock.apk, 115 kB) to your computer.
Make sure your device’s battery still has at least 70% power. You don’t want the device to shut down in the middle of the procedure.
Backup all personal data on your phone to make sure you have a copy of your personal data (e.g., contacts, SMS, MMS, Internet settings, Wi-Fi passwords, and the like) in case the procedure in this guide erases such data.
Copy the GalaxSim Unlock APK file to your Galaxy S3′s SD card.
Launch the file manager app on your device.
Locate the GalaxSim APK file and tap on it to install it on your Galaxy S3
After installation is complete, launch the GalaxSim Unlock app on your device.
Grant it root access by pressing the Grant/Allow button.
Tap the Backup EFS button to backup your EFS/IMEI data.
Your EFS/IMEI data will be backed up in the GalaxSimUnlock folder on your internal storage. Do not delete this folder. We also suggest backing your EFS/IMEI data to a safe place on your computer.
Tap the Unlock button to unlock your Galaxy S3.
Reboot the phone.
Once your device reboots, you should be able to use your newly SIM-unlocked Galaxy S3 on any other GSM carrier. Enjoy! If you encounter any problems feel free to post in the comments, and we’ll do our best to assist you.