Thats always my concern as well... We live 60 miles out of Washington DC and only Verizon works here where I live. Any other carrier you have to do a 'GREEN ACRES ROUTINE" and go outside to climb a pole to use the phone...
It does look like AT&T I think it is is getting better with USA coverage. Sprint is really bad here at the house.
Maybe there is something from the Ancient Alien World buried close-by here blocking the signals...
I sure am getting tired of the higher cost for Verizon service. Also hearing that Verizon is now doing another round of trying to thin out us old timers with grandfathered perks.
Roy Ken