TV in an RV when you are locked into At&t is solvable. T mobile offers to buy out your existing contract. Get their unlimited plan and tether to a computer. You just hook the TV up to the computer using an hdmi cable. We use Verizon. I kept one of my old unlimited data plans and we pretty much now use that to watch TV on the road. Or Apple TV.
We do have a Direct TV HD dish on the top of our bus, but I got fed up with no local channels + no PBS that I cancelled. I have no intention of going Direct again even though I have an almost new HD dish.
The key is having a good source of internet.