[Sprint Samsung Galaxy S 4 Q&A, Help & Troubleshoot] Plague_Bearer:
first I'd like to thank all the different people on multiple forums that put in all the work with what I gathered here to make a simple guide on what got me a domestic sim unlock for my SPH-L720T

I know there are other guides out there, but I couldn't find any clear and simple methods to do this; there were a lot of things where I had to dig and scratch my head for information, so I will post step by step how I did this and try to make it clear and easy. This is all free and requires no unlock service.

I currently have my SPH-L720T on Straight Talk with Talk, Text, Data, everything working. I ran through and made phone calls, texts, picture messages, checked the internet connection etc. All worked with an ATT sim card that came with my Straight Talk Activation kit. I havent tested T-Mobile, or other sims. But i can verify for you the ATT sim from Straight Talk works.

This is what I did step by step and what worked for me, I'm not responsible for what you do.

Step 1

1st off you need to root, this was extremely easy with chainfires CF Auto Root, and it worked on 5.0.1

http://xdaforums.com/showthread.php?p=41743595#post41743595

just carefully follow the directions, it worked perfectly.

Step 2

next you need to flash the MK5 modem

put your phone in download mode (power your phone off, then hold volume down+home+power. their will be a prompt menu and it will warn you, but just continue by pressing volume up),

next open Odin which you should have from the CF Auto Root process, connect your phone to your computer with your usb cable while its in download mode, Odin should recognize it and you should see it says its been added.

Now flash the MK5 modem. You do this by clicking on the PDA / AP button in odin and selecting the "modem-L720T-MK5.tar.md5" file I provided. Make sure the re-partition option is not selected in Odin, now click Start. Odin will run its process and once your phone reboots, I got a quick notification saying that android has successfully updated. Then you can check in your "About Device" settings in your phone to verify you're now on MK5.

SPH-L720T MK5 Modem:

https://www.mediafire.com/?m28qp33jrb7q4zq

Step 3

Next you actually Sim Unlock for domestic use, this is the part that took the most time searching for something that worked, I used the Galaxy Tools .apk app from idone.apps. You can purchase it or obtain it by other means, but just make sure its up to date, v3.1.8. is the version I used

http://idoneapps.com/instructions.php#msl_sam

When you open Galaxy Tools .apk, you'll see a MSL/SPC: number which is your unlock key, you dont need to do anything with this, because on the option / button called SIM UICC Unlock, all you do is click the button, and it uses the MSL number to unlock your sim for you. If you've successfully Unlocked your sim, it will say in bold letters "SIM uicc: UNLOCKED"

If your MSL/SPC says UNKOWN then you probably need to update your Galaxy Tools .apk or reinstall, I had to update mine, then it worked like a charm

note: I know some other people had success with SSU.apk the samsung unlocking app, but it wouldn't work for me, the app would force close, try SSU.apk if you like

http://xdaforums.com/sprint-galaxy-s5/general/sprint-samsung-unlocker-unlock-sprint-t2928250

Step 4

Next you need to modify your GCF settings via the service menu. Open your phone dialer, and follow these instructions

Dial *#0011# and in the service menu do the following

Click (menu) then (key input) then input Q then (Ok)

Click (menu) then (back)

Click (menu) then (key input) then input 0000 then click (Ok)

Wait for about 15 seconds then a menu will pop up, from there follow these procedures:

Click (UMTS) then (DEBUG SCREEN) then (PHONE CONTROL) then (NETWORK CONTROL) then (GCF) then the top option. From there you may press the home button and go to Settings and change the mobile networks to either Automatic or GSM.

note: these directions for the service menu were from user F_X here, http://forum.gsmhosting.com/vbb/f453/how-unlock-l720-l720t-1980164/

Next all I needed to do was modify some settings in the Mobile Networks section on my phone

Change your Network Mode to GSM/UMTS, you can also choose Automatic, but I have it under GSM/UMTS.

Step 5

Lastly you need to add an APN setting so you can actually use your service, for Straight Talk I use these settings

go to Settings, under Mobile Network settings to Access Point Names (APN) and press the + button to add a new APN.

Enter Name: Straight Talk

APN: tfdata

Proxy:

Port:

Username:

Password:

Server:

MMSC: http://mms-tf.net

MMS Proxy: mms3.tracfone.com

MMS Port: 80

MCC:

MNC:

Authentication Type:

APN Type: default,admin,fota,mms,supl,hipri

Keep default values for all blank fields shown above.

Press menu button (top right) and select Save.

note: these settings I got from here, https://apn.gishan.net/settings/752_11_straight_talk_apn_settings_for_samsung_galaxy_s5.php

If you already have your Straight Talk Simcard in, then you should literally see the 3G icon and everything active almost immediately, it was for me at least.

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Thats it, you should be good now. Some other notes I would add, would be that I THINK, and I repeat THINK, you can lose your SIM UICC UNLOCK in Galaxy Tools .apk if you flash to another ROM or upgrade your OS, I never really found a clear answer on that, so I am leaving this phone with the stock ROM so I dont lose my SIM Unlock, but please share if you know more about this.

Also please share more info so I can update this Guide if you have more knowledge, which I KNOW theres more info out there on this to be added. Or if theres a mistake in my guide lol (pretty sure I covered almost everything I did in my own process.) I dont know if this will get moved or what, but it will prob be associated with the section about unlocking in the [q] ALL THINGS GALAXY S4 (GS4) MODEL SPH-L720T under the "UNLOCKING FOR USE ON OTHER CARRIERS" section here, http://xdaforums.com/showthread.php?p=56584245#post56584245

Again thanx to everyone I sited, seriously..!

-Ømar