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. galaxy s4 fix calls to voicemail connection issuesgalaxy-s4-vs-galaxy-s4-mini 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: