Hi,
New here and I don't know if you are still trying to unlock your phone.
If you mean GSM unlock your Sprint S4 mini, you can do it if your phone is currently activated on Sprint. Ask them for your network unlock code and then have Sprint World Wide CS unlock your phone. Last year when I traveled overseas I was told that the S4 Mini could not be used on GSM carriers, but it can. I was able to activate mine on a TMobile MVNO. I unlocked it myself, but the rep said that if you have Sprint unlock it for international travel the same code works for domestic GSM unlock. Permanently. (I don't know if it's separate procedures for domestic vs. international unlock.) Hope this helps!