Cannot connect to cellular provider after installing OREO

[Android Central Question]

Hi - I bought a Samsung S7 Edge in UAE, model SM-G935FD and serial # RF8J10HRBXJ. I recently dropped the phone (cracked screen and then the audio on calls did not work as part of repair) and took it to small shop who seemingly rooted the phone and installed marshmellow. It now moans at me that it is rooted "unauthorized action" which I cannot remove. I tried flashing samsung stock OREO firmware for South Africa via ODIN (in ODIN I tried AP first and then BL, AP,CP and CSC but same result) and everything appeared fine but ZERO cellular provider connection possible - I tried Smartswitch but it told me "unauthorised" or similar.

I am suspecting a potentially related issue may be one of the parts replaced was network locked but dunno if its the real issue here...

 

[Alessandro Vignazia]

And I took it to Samsung but they said because its a UAE phone they cannot do anything in South Africa to install the software </sigh>