I battled the data demon when I was a Verizon customer. I had to learn more about how it works, what uses large amounts of data, and how it's reported. How to view usage on devices is helpful.
Cellular devices have settings to limit or turn off data.
There is lots more to know if you have specific questions
(The following is included after all posts to save typing) I don’t work for AT&T. My replies are based on experience and reading content available on the website. Our answers are honest, but not always appreciated. If you posted personal information, please edit and remove.
*The views and opinions expressed on this forum are purely my own. Any product claim, statistic, quote, or other representation about a product or service should be verified with the manufacturer, provider, or party.