How To Unlock AT&T Samsung Galaxy S 4

But if you already have an AT&T Galaxy S4 and you aren’t locked into a contract, you can easily use that phone on other’s network. The process is simple, but requires a little setup, and for some, sacrifice. Thanks XDA Forum Member sush143555 shared a method to SIM-Unlock the AT&T Galaxy S 4.

1. Launch the Phone app on your Galaxy S4, and dial in: *#0011#
2. Press the Menu button followed by the Back key. Then, hit the Menu button again and select KEY INPUT. Enter 1 and press the OK button to enter ServiceMode.
3. Press Menu one more time and tap back again. This will pull up the Main Menu for ServiceMode. Tap [1] UMTS.
4. Now select [1]DEBUG SCREEN, followed by [6] PHONE CONTROL.
5. From the next screen, pick [6] NETWORK LOCK.
6. You’ll get three options. Hit the one that says [3] PERSO SHA256 OFF.
7. Now, you need to get back to Main Menu. To do this, hit the Menu button followed by the Back key. In Main Menu, now pick [6]COMMON, and then [6] NV REBUILD.
8. The phone will tell you that a Golden Backup exists. Tap [4] Restore Back-up.

Your device will now go through a series of “conditions”, where it will first freeze, then get on a black screen with Blue LED on and both capacitive buttons on, after which it will reboot automatically. The whole cycle might take a couple of minutes, so be patient. Once it powers back on, it’s network unlocked, permanently.

Source: XDA