[Samsung Galaxy On5 Questions & Answers] estebangtz:
This is what I tried with CG Pro Key

I read online that it is done with the same method as the SM-G550T1, so I am trying it on a SM-G550T2 this precise moment. I am not responsible for any problems that may arise with your phone if this does not work for you, I have tried it on several SM-G550T1 from Metro PCS and it has worked well.

1. Power on phone, go to apps>settings>about phone, then tap on Build number seven times to enable developer options, once message prompts about being a developer.

2. Go back to settings and look for the "developer options", go there and make sure "OEM Unlock" is selected, as well as "USB debugging".

3. Download the following three files, I tried posting the download links but since I hardly ever post upon forum policy I am not able to, if you need the files PM me.

3a. Odin 3.10.7 is the version I have used and has worked for me

3b. TWRP custom recovery, should be installed Using Odin. Put phone in Download Mode (Home+Power+Vol-) and connect to computer then open Odin.exe using right click and running as administrator. Once opened select the "AP" box and select the TWRP file, then click on start, once Odin finishes it will restart phone. Once this happens remove the battery, because I let it fully restart once even after Odin showed the PASS, and when I tried entering Recovery Mode it went into OEM Android recovery.

3c. SuperUser Root. Once the TWRP custom recovery has been installed save the SuperUser file in an SD card and insert it on the phone OR save it directly to your phone's internal storage, then put phone in Recovery Mode (Home+Power+Vol+). Once in recovery mode you will get a screen with a disclaimer, just "Swipe to Allow Modifications", then select "Install", then on the bottom "Select Storage" and go to wherever you saved your file and select it, then "Swipe to confirm Flash" and wait for phone to finish, then select Reboot option.

UP TO THIS POINT your phone has a custom recovery and SuperUser access, I have only unlocked these phones using GC Pro since its the method that has worked for me, but theoretically you could be able to test with z3x o octoplus, Processor is Exynos from what I have read on other forums it should work using models g920t o g925t, but I haven't tried that so I can't vouch for these to work. IF YOU PLAN TO DO SO, DO IT AT YOUR OWN RISK

4. Connect your GC pro Key or Box as well as your phone, and open GCPROGSMTOOLKIT. Once program starts go to Samsung tab, select any of the models, it does not make any difference, then under "Service" select "TMOBILE Unlock" and click on "Start", the phone will prompt for computer connection, then will ask for permission fomr SuperUser, Grant it then sit back and wait, the box will finish and restart phone:

Using Version...1.0.0.0047

Selected Model GT-I5503

Selected Task SAMSUNG T-MOBILE UNLOCK

Searching ADB device Please wait..

Device Detected...

model:= SM-G550T2

Androids Version:= 6.0.1

Description Version:= on5ltetmowal-user 6.0.1 MMB29K G550T2UVU2AQC4 release-keys

Platform:= exynos3 [ universal3475 ] [ SHANNON308 ]

Baseband:= G550T2UVU2AQC4

VER:= G550T2UVU2AQC4/G550T2TMB2AQC4/G550T2UVU2AQC4/G550T2UVU2AQC4

Carrier := TMB_USA

AP UART Status := Disable.

Security Patch := 01-03-2017

Network Mode := LTE

Simstatus:= ABSENT

ANDROID-ID = 920110f5341e24df_0000D5E046

SU Version..2.77:SUPERSU

Device is Secure Rooted..uid=0

System Permission is Read/Write...

SAMSUNG ALL T-MOBILE UNLOCKING STARTED...

Checking Data...

Waiting for Loader...

Loader Ok...

Direct Unlock Success...

!!! Success !!!!

Restart Phone Manually if not done auto...

Total Time Take...00:00:09

Log Saved

Afterwards insert a SIM card and enjoy your unlocked phone, I just did it as I typed all the process for you on a Wal Mart family mobile SM-G550T2 and it worked no problem, hope this is helpful to you