Has anyone solved the problem of unexplained data usage spikes that so many people have reported?

I, like so many other people, noticed a sudden increase in data usage several months ago.  I've paid over a $200 in overage fees since this started.  I bought a hardware firewall to break down all traffic by device and app, and discovered a Google service downloading over 100-200 GB almost daily, sometimes twice a day.  Quitting Google Drive stopped this, and it remained stopped after restarting Drive a few days later.  So, I seem to have resolved this particular issue on my own.  However, today and last month I got the "You've used 75% of your data" message.  Checked the Xfinity usage meter and it thinks I've used over 900 GB of data this month.  My firewall shows around 200 GB of total traffic.  [Edited: 'Language"] ?!  Has anyone gotten a clear explanation/solution to this [Edited: 'Language"]?!  Having my firewall data in hand, I seriously think Xfinity is doing something to rip us off.