A T& T and Verizon

I've had att for a long time and was considering Verizon because friends that we traveled with seemed to have better coverage. This year, several times I had service when they didn't. Years ago, I had a 'trucker' antenna mounted to the rv. When camping in remote areas, people would borrow my phone to make calls. When I could not find a phone with an external jack, I ditched the antenna.
I recently got a wireless home phone to save money and I take it with us when camping. I thought about looking into the possibility of getting another outside antenna to mount to the top of the trailer.