What is going on with data usage?

Every month Cox is saying we are using more data - when in fact, I've had two young adult gamers move out of the house, so now it is just myself and a young adult who is either working or at school.  I have been chatting with a Cox person (Candyece N.) and she cannot tell me what devices are using the data nor can se tell me what time of day the data is being used.  She also does not understand the difference between a modem and a router.  I am so frustrated. For eight (8) years, my data usage has been between 400 GB and 600 GB, never once over 700 GB, not once. Before the new system, my data usage was flat - eight years of flat usage; now with two less people in the house (neither of us gamers), my data usage is going up monthly (582, 699, 713, 934 GB and rising).  Their solution is to simply tell me to upgrade my plan. I then asked how to opt out of the automatic 50GB blocks (as it is only one day before we reset) and she told me "The internet cannot be turned off."  I pointed out that they do it all of the time for people who do not pay their bills.  She said that opting out is not an possible.  Why not? How can it be possible that my data usage can go up so much in such a short period of time with less people in the house? Candyece then told me call the Abuse department, which I did and they told me that they had no idea why she told me to call them that they cannot tell me anything more than Candyece did.  How can we believe Cox's numbers if they cannot tell us how they arrive at them?  Is this happening to anyone else?