Data Usage By Device?

My monthly data usage was 656 GB, 912 GB, then 2104 GB - with the spike after 2 kids went back to college.

I'd like to find usage per device so I can see if there are any problems or rogue devices.

I tried calling and was routed through a never ending circle of an automated voice menu.

I tried chatting with an agent, which told me to call a different number but I got the same never ending menu.

So I tried "have an agent call me" and I got "You should receive a call from us in the next few minutes" but waited over an hour and got no call.

I am frustrated beyond belief with the lack of service/responsiveness. 

Please tell me how I can see data usage per device so I can check integrity of device/network?