Software to monitor ISP bandwidth usage

Are there any (preferably free) windows based programs available to monitor internet usage? A few months ago, ATT began capping internet Uverse data at 1 TB per month. Since then, we have been coming close to, or slightly exceeding this cap and would like to avoid paying any overages. My kids use Netflix and Amazon prime for TV watching as we do not have any other TV subscription services so I know our data usage is going to be quite high, however, the "daily report" that ATT provides on overall data usage seems suspect. I would like to be able to see which devices in my home are using the most data. We have a mixture of wireless/wired devices (windows pc's, macbooks, iphones, ipads ect).

Ideally, it would be nice to see real-time usage as well as totalized usage. I am not interested in seeing any intranet traffic, rather, just traffic traveling through, to and from the ISP. If its any help, our router is a Pace 5268.

Thanks!

I think the only way(s) you will be able to do that is either though your router (if it offers that functionality) or by building your own router (pf sense, sophos, etc) and passing the network through it to record how much data is being used. Installing a piece of software on your computer won't do much unless 100% of the traffic goes through your computer.

Here's a good article on this subject How to Monitor Your Internet Bandwidth Usage and Avoid Exceeding Data Caps

log into att uverse's website and login to your account, the summary page shows right there where you are at for the month.

i use pfsense and the traffic according to my router seems to match what it att.com says. bear in mind they account for both upload and download traffic.

I use a program called NetWorx v5.5.5 on my tablet. It's freeware though the softperfect site's newest version 602 isn't.
https://networx.en.uptodown.com/windows
I run it for the taskbar in/out info icon to save desk real estate. It does quotas but I have no need for that atm.
I don't let it update obviously and block just the exe in fw. BatteryBar is another great taskbar tool.