How do unlock Sprint galaxy S4 SPH-L720t

[jetski3021]

I have rooted the phone successfully and now I am told I need to downgrade modem as it is on 5.0.1 lollipop in order to unlock. Does anyone have any procedures for doing these next couple of steps?

 

[gooch1006]

I have been searching for days, one forum then another. the quickest way is pay about 10$ on a auction webite for an instant unlock, it will actually take an hour or more, but its permanent and guaranteed .