Cellular data usage doesn't add up

I'm on the newest iPhone software: 11.1.1

I have a work-from-home job and it is rare that I leave the house. When I'm home all my electronics are connected to WiFi. I don't watch Netflix on my phone, I have my TV for that. I checked my "cellular data" usage and it said that from May 22nd I have used 147 GB's. Sounds pretty good. Except that my boyfriend just went into AT&T and informed me that for the month of October I used 85 GB's and for the month of September I used over 50 GB!

Now, something isn't adding up here and I am not exactly happy. What the **** is using that much data and why is my iPhone giving me a drastically different data usage number than my actual provider? Not to mention as of halfway through November's billing cycle I've used 2.35 GB according to AT&T. What is going on???

Also, why can I no longer see exactly which apps are using the most data? It used to say right under the app in Cellular but now it doesn't.