Using iPhone 7 plus latest firmware. Same issue on iPhone 8.
Not a biggie just an interesting observation :-)
the spark coverage map shows very limited coverage in that area and skinny shows the same thing (being the same network and all)
One of the problems all networks face is how to get backhaul to remote sites. You can't magically get Gigabit backhaul over a long distance links using DMR!
the 4g off the rainbow mountain sight is 700mhz, so could be for RBI only?