NAT setting,port forwarding/Xbox one


Hi all I'm trying (getting angry) to get the NAT setting off strict on my Xbox one,to explain I'm using a three SIM card in a tp link mr6400 router,I'm wondering if anyone has any ideas/help on how I am to do so as it's stressing me out. I have an average understanding of what I'm doing but it's not going to plan.thanks in advance