When it comes to unlocking Samsung is not that badass such as Apple, on Samsung there are many methods. Some methods are paid, but some are free and when it comes to Apple there is no words such easy or free. Well let’s get to the main point today i’ll guide you how to Sim unlock AT&T Galaxy S4 SGH-I337 and Canadian SGH-I337M. In this method you have work in developer’s menu so if you think its difficult then you can use paid services which I don’t agree with. This guide is only for AT&T Samsung Galaxy S4 SGH-I337 and Canadian SGH-I337M, for other variants like Galaxy S4 I9500 and I9505 you have wait for few days. Now let us proceed to the process.
Also See: Sim Unlock Galaxy S4 I9500 and I9505
- T-Mobile Galaxy S4 SGH-M919
- AT&T Galaxy S4 SGH-I337
- Canadian Bell, Rogers, Telus, Virgin Galaxy S4 SGH-I337M
- Galaxy S4 GT-I9505 LTE
How to SIM Unlock AT&T Galaxy S4[ SGH-I337 and SGH-I337M ]:
Step 1: Open your Phone dialer.
Step 2: Type *#27663368378#. [ If its not working then try *#0011# ].
Step 3: select  UMTS and Tap on it.
Step 4: Now tap on  DEBUG SCREEN.
Step 5: Now You have to select  PHONE CONTROL.
Step 6: Tap on  NETWORK LOCK.
Step 7: Now Select  PERSO SHA256 OFF.
Step 8: Now tap on SHA256_ENABLED_FLAG.
Step 9: After tapping on SHA256_ENABLED_FLAG. You see the following message.
Step 10: Tap on the menu button to go back to the menu.
Step 11: Now you’ll be in NETWORK LOCK press back again and again until your return to the main menu.
Step 12: Tap on  COMMON from the Main menu.
Step 13: Now tap on  NV REBUILD.
Step 14: In the NV Rebuild tap on  Restore Back-up.
Step 15: Now your device will freeze for few seconds and then reboot your device.
All Done !!