I’ve been using T-Mobile for years. No problem around town, but not so good out in the boonies. Most providers will have a place you can go on their website and check the coverage for your specific area.
I’ve been looking at the coverage both nationally as well as internationally.
According to what I’ve read, Verizon has the best coverage nationally.
AT&T is pretty close, and their international coverage is great.
We live in the boonies, which is why my cell reception isn’t great. I’m hoping the upgrade will make a difference.