Set AT&T’s router to bridge mode.

If you want lower ping, you have to switch to a different type of service like fiber, cable, DSL, or even cellular. If you’re out in the middle of nowhere where none of those other options are available, look into Starlink because even though it’s satellite internet, the satellites are closer to the earth so you get latency similar to what you would get with a cellular connection of about 50ms instead of several hundred ms with a traditional satellite provider like HughesNet or Viasat.