I use T-Mobile but have not been "Mobile" in a while.. They recently (2015/6) upgraded service in many areas.. I can ALMOST use my phone where I'm currently "Stuck" on their towers (works on Wi-Fi... When it feels like it).
HOWEVER: Where I'm stuck the park Wi-Fi is great.
now, normally in the winter I spend my time between 3 campgrounds
One has decent Wi-Fi (not great but I can often stream a video late at night, well one hour a week plus one hour a month) The other two Fantastic T-mobile coverage (Yippie)
Summers it's not so good.. but I'm hoping the improvements will make it better.
I park EAST of the Mississippi however most of the time (planing on changing that either this year or next).
With luck this time next week I'll be "parked" where the Wi-Fi I have yet to netotatite but the T-mobile works (at least it did when I visited the shop).