Apple, copying others and calling it magic since 1976!
I've done this before and I just taped them to a business card with the name of who they belong to next to the sim. Easy Peasy.
I mean T-Mobile markets. You can read more about NSN setup here.
It should sound similar, unless you're talking to someone who's on Verizon using Advanced Calling, then it should sound similar to the regular VoLTE network.
About the mountain roads, yeah,...
I've used a couple of GoPhones on my NET10 byop simcard - latest one is a Nokia/Microsoft 640 win phone... works wonderfully.
I don't know about paying H2O directly, but I have heard that you can set up a RTR (autoload) payment to H2O with CallingMart, and set the timing (number of days). For instance, one could make...