Default [Q] Carrier unlock for I9500, binary counter and knox

Hi guys, I wonder if I can get some help unlocking my I9500. I'm traveling to US next week and would be acquiring a t-mobile or at&t prepaid sim to use the the phone, so I need to unlock it.

First of all, I have verified that my phone is locked to accept sims only from my carrier.
Second, yes, I have tried the methods explained http://forum.xda-developers.com/show....php?t=2282683 , but I always get:

MENU NOT EXIST
PRESS BACK KEY
Current Command is 111

If relevant, here is some info from my s4:
android 4.3(official from my carrier)
baseband: I9500BUEMK1
build number: JSS15J.I9500UBUEMK1
AP: I9500UBUEMK1
CP: I9500UBUEMK1
CSC: I9500UWMEMK1
RF Cal: 2013.4.24
HW Rev: MP 0.800

I don't want to use any method that may void my warranty, or that alters the binary counter or the knox flag.

Are there others "non invasive" methods to carrier unlock my 9500?

If I have to get a network unlock code from some site in the internet, which ones do you recommend that are reliable? would using a unlock code alter the binary counter or knox flag?

Thank you so much in advance.