You or a family member is new to cellular service and likely starting out with limited usage, and need help with setup and using service:
I'd probably send them to a Cricket store. Cricket is a great place to start. Cricket is virtually the same as ATT's native network without roaming. In short, they have outstanding nationwide coverage.
No contract service. If you end up not liking them, you can quit at any time.

Traditional Options:

The big carriers no longer require contracts. Give a family member or friend your old phone. They can get on the best networks (Verizon or ATT) for a relatively low cost.

Other Interesting Low Cost Options:
- Ting (www.ting.com)
- Republic Wireless (https://republicwireless.com/) These folks have a very low-cost service which works best for folks with a smartphone and use it primarily in places that already have WiFi access.