I have a Google Fi phone which switches between the Tmobile, Sprint, or available wifi networks, depending upon which is the strongest. And it works for free in Europe (and the rest of the world, too). It did lose coverage in parts of the mountains in MA, but to be fair, so did my old Verizon phone. Coverage via Sprint seemed to be slightly better than Tmobile. I don't actually use much data, and you only pay for what you use, so my monthly phone bill is around $25. Unfortunately, iPhones don't work.