I have never used more than 350 gigs in a month, but today I received an email that I am approaching my max. I live alone and have never shared my password with anyone. None of my habits have changed since my usage went from a few gigs per day to more than 30 on most days, even on weekends when I have been away. I checked to see which devices have wifi access and all of them are mine: phone, PC, thermostat, security camera (which hasn't even been on) and Ring doorbell. Customer service told me there's no way to determine how much data each device uses, which is not true. I can check Windows to see that my PC used 9.41 gigs, my phone used 26 gigs. The doorbell uses about 200 megs and the thermostat about 50 megs. I do watch Netflix on my Firestick but never more than 10-12 hours/week. Even at the highest resolution, I should not have upped my data usage this much.