The dial code works for my AT&T SGH-I747 S3. My ROM is the most current Samsung stock 4.1.2 update, baseband I747UCDMG2. But my NETWORK LOCK menu is different than the example. My menu item number 4 in NETWORK LOCK is "RAT FREE SUPPORITNG ON" (sic). I don't have the "NV Data INITIALLIZ" menu item, before or after selecting "PERSO SHA256 OFF". I've looked in all the other menus and submenus, but haven't found anything that remotely looks like "NV Data INITIALLIZ".

How To: Network Unlock Your Samsung Galaxy S3 to Use with Another GSM Carrier

The NETWORK LOCK menu item "1 PERSON SHA256 Info" says, "SHA256 ENABLE FLAG 0", which seems like the lock should be disabled, since 0 is usually "off/disabled" and 1 is usually "on/enabled".

I also looked at the main menu item 4 "SIM" and found "CHECK NV". The CHECK NV output says, "Brand Pref: Unexpected value. RTRE Configuration: SIM based. FTM Mode: Online Mode. ENS: Enabled. UIM CLASS: UMTS."

But when I inserted a Sprint SIM, I was still asked for an unlock code.

Any ideas what I need to do next?