Hopefully the OP is going to take the steps to narrow it down. Netflix in low definition doesn't use that much. Perhaps 300MB per hour. That's perfectly fine for light viewing.
The OP probably doesn't know about Glasswire. Overall, when it comes to the general internet using public, few people do. You have to give people the benefit of the doubt and help, not question why they haven't already done something or don't have something installed.
This person was actually quite polite and didn't rant. He/she just asked questions and asked for help.