OK, Is this 4K UHD? If so, it would eat that much. Try setting your TV Netflix back to SD quality.
So this is going to sound crazy, but here we go. I've been going over my bandwidth cap for the last few months - significantly higher usage than normal. I've been keeping an eye on it - with today being my best illustration of the problem.
According to my router, today my TV drew 2.1GB of data - but the issue - it was only turned on to confirm the usage through it's mac address.
This pattern continues - a night where Netflix was streaming for 20 minutes, the TV used 8gb. A night when we were home for no more than 4 hours (not all that time spent on Netflix) - 21gb used, all showing as TV from the router.
Please help! My ISP is fully useless thus far, recommending I unplug my router for 24hrs, then monitor usage. Tough when I'm attending an e-course from home for the next week.
If this was mine I'd change my WiFi SSID, change to WPA2 AES personal security and go into lockdown. That is, don't allow anything to connect for a bit to see if the logs show activity.
Given how easy it is for me to use your WiFi if you have it on WPA or less security plus how I can change my MAC address to match your TV I could be right next door eating up your bytes.
Time to change that SSID and be sure WiFi is on WPA2.