@Taymay 

Hey

This is a common enough issue

The cause is the NAT between your T Mobile and A7.   What you need to do is..

Find the PS5 ports you need to forward (say 12345)

Log into the T Mobile router, create a port forward for port 12345   to   the A7  on Port 12345

Repeat for other ports (you can likely do ranges)

That should then sort the issue by forwarding anything on 12345 straight to the A7..  if you are still getting NAT warnings then you can do the same on the A7, this time forwarding to your PS5 on 12345

Therefore   comes in on 12345     T Moibile forwards it to  A7 on 12345       A7 forwards it to PS5 on 12345...   that removes NAT completely for that specific port.

Hope that helps!!