OKAY.....so Ive spent days, and hours trying to unlock my sprint samsung galaxy s4 L720PUBNC6 BUILD/ android 4.4.2 to use for straight talk. I had an S3 and pretty much have all US S3 variants mastered. I was able to get in to service mode by dialing *#0011#. I pressed back, key input"Q", and key input "000000" waited about 15 seconds. I used the instructions from this post to change the settings, but nothing happened. I used several others post from various forums to try, and get the MSL/SPC code. MSL reader, and get my MSL apps did not work. regionlock away did not work, and neither did SAMIOTA hidden menu app. If you download MSL utility.apk it will give you your SPC code. The question now is what options to change? I still get the invalid sim message, and so far no service. I did get a breakthrough of sorts....my phone tried to set up on ZACT Mobile. which is apparently sprints version of a prepaid network. If someone can help figure out the options needed then we can master this device, and move on to the S5.