Note 8 N950F, works on all networks except 1?

So I did the screen and charging port on a Note 8, everything went fine but the customer came back and is stating that they cant make or receive phone calls, I have tested with other networks and they all work fine but when I put a sim from his network in it says its connected (registered, full bars and internet) but will not make or receive calls text's or use data, as soon as i hit call the data drops away and it loses signal. Tried a different port assembly, forcing it to use 3g over 4g, 2g is not active in my country. resetting settings factory resets etc.. but nothing helps, In the field test hidden menu it reads normal as far I can tell, I compared it to another note 8 we have here on the same network and it was the same. Has anyone had any experience with this sort of issue? or found a fix? Thanks