Well I had some issues last week with attempting to unlock an I9300T (same as I9300 only it picks up the 2400hz band from the Telstra service provider) anyway,eveyone was mentioning 'Just flash back to ICS to downgrade the bootloader, unlock and flash back again' or something along those lines. Needless to say the first thing I did was root the phone to back up the EFS/IMEI and in the process of rooting via Odin with CF-Root....the task in it's self bungled the EFS anyway. So corrupt EFS, no signal and IMEI displaying as 0049. On a side note I discovered a new and much easier way of recovering your EFS should anyone run into those sorts of issues.
It was told following tutorials from various sources that the Service Mode menu input for simlock works on international SGS3 models???? Well apparently it DOESN'T....so all my effort was wasted I guess? Flashing the phone and bricking it several times. Anyway my point I wanted to make was that there is quite a difference the Service modes available for Australian/International I9300 devices.
I am curious to know (if possible?) transplanting the serviceModeApp.apk from a device where Network unlock can be performed by simply pinning in the service code via the dialer....to un-sim-lock the device??
Would somebody who has successfully unlocked their I9300 via this method be willing to share their serviceModeApp.apk for me to be able to test this theory??
EDIT: Needs to be Android 4.1.1 from what I have just read now?