Sim unlock Galaxy S4 GT-I9505 UK

Try this method with your authorized sim in your phone.   This method should work for all U.K. Galaxy S4 variants for Orange, O2 etc.

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1. Dial *#0011#
2. press Menu then tap BACK
3. press the Menu again the tap KEY INPUT then enter 1, (wait a few seconds) it auto jumped into service menu.

4. press Menu then tap BACK (not needed for me)

Your are now in the SERVICE MODE MAIN MENU

Tap [1]UMTS (may auto go into next menu (mine did)

then [1]DEBUG SCREEN
then [6]PHONE CONTROL
then [6]NETWORK LOCK
then tap [3]PERSO SHA256 OFF

Go back to the UMTS MAIN MENU by pressing Menu then Back (several times)

then tap [6]COMMON

then [6]NV REBUILD (if this does not work next time)

do [4]RESTORE BACK UP

the device will freeze, black screen, Blue LED Light, Menu and Back key ON. Wait for it to reboot (about a minute).

Your Samsung Galaxy I9505 is now Sim-Unlocked.

When I booted back in with AUTHORISED sim, I had to turn off Mobile Data, then turn it on.
I then turned off the phone, put my UNAUTHORSIED Sim in, booted back up and NO NETWORK PIN request!

Again, I had to turn off Mobile data, then turn it back on. The UNAUTHORSIED Sim worked!!! 

My previously locked to Three UK GT-I9505 is now unlocked to all networks  Thanks again to XDA (Y)

It has been reported that this is indeed a “permanent” unlock: