Unlock Samsung Galaxy s4 Sprint Sph-L720T Invalid SIM

I have a Galaxy S4 SPH- l720T model and need to unlock it .
I read a post that this model can not be unlocked(xda in 2013).
Does anyone have this model and managed to unlock it?
Here are some model specifications :
Galaxy S4
Model SPH- L720t > Triband<
Sprint
Android Version: 5.0.1
Baseband version: L720TVPUCOK3

Sorry my Google Translate english.