Data Usage Overage. Doesn’t make sense

Is there a way to see a daily usage? Or which device is using more data? 

After 1 year and 9 months of service, I went over my 1.2TB data limit. With the previous months going from:

March: 632Gb

April: 861Gb

May: 1017Gb

June: 1234Gb

Its ridiculous. Data usage habits do NOT change on our account. No new devices added, standard amount of streaming and gaming. How is my data usage increasing at a linear slope? 

After calling Xfinity and Inquiring about the odd increase of data, It was used as a sales pitch to purchase “unlimited data for an additional $11/mo”. And that there was no way to see the fine details of data usage. Essentially, ‘this is the number we are telling you that you used’ and there is no way to troubleshoot a reason behind high usage. 

It doesn’t make sense. Would love to speak to a technical person and have them explain the details to me other than a customer service rep.