I have sucessfully rooted a couple of them using the same method which is the following. I downloaded the TWRP recovery for this phone (SM-G550T1) or (on5ltetmo). I then usedtoto ODIN to flash the recovery to the phone. That essentially unlocks the recovery and the ability to flash the phone. You then need to download the .zip file for SuperSU on to your phone and reboot into the TWRP recovery on the phone and flash SuperSU that's what actually roots the phone. Then don't forget to install busybox after you reboot the phone.