How is service in Ventura County, CA?
Moderator’s note: post was edited to provide searchable content.
Go to this map, select the samsung s7 as your phone, and drop some pins in the areas your frequent:
4G LTE Coverage Map | Check Your 4G LTE Cell Phone Coverage | T-Mobile
In my experience their “fair” coverage rarely works indoors.
Look around where you live, work and drive. If there are no T-Mobile stores, that may a bad sign and you should do more research. Ask your friends, neighbors and random people with a cell phone about their experience with wireless service providers.