Look into Google Fi. They have contracts with three carriers and the phone automatically switches to the one with the best local signal. Also, if you travel much out of the country the same holds true with international carriers with no additional charges. You can buy a phone directly from them or get a Sim card if your current phone is supported.
I use their flexible plan and keep my data to under 1 gig per month. Google will also automatically shift to a web based phone if you are using a WiFi already in their plan (like Srarbucks) or you can link into free WiFi too.
I was a Sprint customer for years until I wanted a Windows phone and they didn't have one. Went back at one point and the service was so bad I said never again.
https://fi.google.com/about/?gclsrc=aw.ds&&gclid=CjwKCAiA1fnxBRBBEiwAVUouUhNCn4tDd0BCab55GgHO8GN2X48u9Z6-eKAKYN1uE36z1rPkHj7t9hoClMQQAvD_BwE