I did this on both a 4.4.1 galaxy and a 4.3 galaxy- one one NAE and one on MK2
First, for anything to work your modem must be an older one, like version MDL. Download the file SPH-L720_MDC_Modem.exe which is a one-click
Odin .exe that will flash ONLY your modem to MDL.
Steps- put into download mode by taking the battery out and putting it back in. Hold the volume down button, the home buttone and then press the power button. When it vibrates, let go. Press volume up.
Run the SPH-L720_MDC_Modem.exe odin one-click installer.
Connect the usb to computer from phone
when com or whatever shows up, press start.
Now, for the domestic lock to work you first need to do the international unlock @ http://forum.xda-developers.com/show....php?t=2415587
It's real easy and explained well at the link above, but I'll run through it quickly anyways.
Download the s4unlocker installer from the post linked above.
Put your phone into diag mode by dialing ##3424#. Press Qualcom button and select the bottom selection.
connect (if it wasn't already) usb from phone to PC
You already installed the proper samsung drivers, right? If not, you'd better do that now.
Okay, now run the s4unlocker and press the scan and unlock button, then wait for the phone to reboot.
Now for the Domestic Unlock part.
Follow the directions at http://forum.xda-developers.com/show....php?t=2530610
I'll run through it real quick, too because there were a few things I wanted to mention.
dial *#0011# (or #*0011#, I can't remember)
when it comes up "No service", press the menu key on the bottom left of your phone. This brings up a menu (wow!), on which you should press "back"
Now press the menu key again and in the menu select "key input" A box will open up asking for you to type in something- enter a "1" and then press the enter key BEFORE hitting the OK button. Mine would not work unless I did this.
Now wait, sometimes it takes a good couple of seconds to give you the menu. Follow the rest of the directions from the above link, setting all the settings to what is stated. EXCEPT where he says to set all the preferences to WCDMA ALL, GSM ALL and LTE ALL. When I selected one, however, an asterisk appeared after my selection leading me to believe that you can only select one of these and so I set mine to GSM ALL and left the others alone. This worked for me, so I thought I'd mention it.
Now that you've manually rebooted after following the directions, you still have to edit your build prop to allow you to edit the apn settings. To edit your build.prop you must be rooted so root with CF auto-root http://autoroot.chainfire.eu/ download the proper one for the galaxy s4.
It's just an odin flash, so enter download mode
load up odin 3.x
hit the pda button and select the cf auto root tar
After rooting I found that one time I had to do some of the service mode settings again and one time I did not, so I mention it here even though I think I had to because of some other error I had made at the time.
Go to play store and download build.prop editor and APN settings Shortcut
Load the build.prop editor and add these two lines to the end of the file
Now reboot manually
add the apn settings widgit to the main screen and open it
click on menu and add an apn
Enter the apn settings for your carrier here. They're all different,(the carriers) but you can find them(the apn settings) easily with google, since they (carriers) all post their apn settings on their webpages.
Don't forget to save the apn settings.
Now select it.
Now reboot, since it couldn't hurt, right?
If you've done everything right you should now have an domestic and international unlocked Sprint galaxy s4. Enjoy.
I suppose you could now reflash the new modem back onto the phone, but I don't have firsthand knowledge whether this works or not- I've only read that others have said that it works. Remember, ONLY FLASH THE MODEM, the rest isn't necessary and will probably knox you all up
All I did was list these things- credit goes to all those who were linked in the above post. Thanks for all you do.