Watch that the phone is locked. Embed the SIM card for the new network to watch that the phone is locked. Numerous S3s are really unlocked out of the case, so checking first can spare you a considerable measure of time.
Overhaul your phone. Your phone must be running Android 4.1.1 (It doesn't work with some Android 4.3 either) or later all together for this system to work. You can check your gadget's rendition by opening Settings, and after that looking to the base and selecting About Device. Search for Android Version to discover your rendition number.
To upgrade your phone, open the Settings and afterward look down to About Device. In the following menu, select System Updates and after that Check for Updates. Your phone will endeavor to redesign over the network consequently.
Perform the network upgrade over a remote network, subsequent to your new SIM doesn't have any availability yet unlock galaxy s3.
Guarantee that your phone is a GSM phone. You can't unlock S3s that keep running on the CDMA network. In the US, this is Sprint. AT&T, Verizon, and T-Mobile all keep running on the GSM network, which permits you to SIM-unlock the phone.
This technique is not ensured to work with all forms how to unlock galaxy s3 yet you will do no harm in attempting.
Open the dialer. You should enter a code in the dialer to open the Service menu. Once the dialer is open, enter the accompanying code: *#197328640#
Tap [1] UMTS. This will open the support primary menu. In the event that you select the off base alternative, press the Menu catch on your phone and select Back.
Tap [1] DEBUG SCREEN. This will open the Debug menu.
Tap [8] PHONE CONTROL. This opens a menu permitting you to alter the settings of your S3.
Tap [6] NETWORK LOCK. This controls the SIM lock capacity.
Tap [3]. After you select this alternative, hold up around 30 seconds.
Press the Menu catch and select Back. This will return you to the NETWORK LOCK menu.
Tap [4] NW LOCK NV DATA INITIALLIZ. Hold up around one moment in the wake of selecting this option. Reboot your phone. After you have held up around a moment, reboot the phone. You won't get any affirmation that the procedure worked. On the off chance that your phone interfaces with the new SIM card's network, then the unlock procedure worked. For more information visit here: http://unlocksource.com/