You can use a router that has a good data management app, or with a Windows computer you can an app called Glasswire. Glasswire is available free at https://www.glasswire.com/
Glasswire only monitors the computer it is installed on, if you have multiple computers it must be installed on all computers and the daily totals added up. It does not detect any other internet traffic used on other devices, TVs, DVRs, Blu-ray devices, X-box or smart phones.
I have a good router, and that gives me all the information I want, by devices and where the data was used.