Data usage going way over average after Fiber installation at new house

Hello,

Every time I have talked to a Cox representative they don't believe me when I say that I've calculated all of our individual device data and it has gone nowhere near what Cox is reporting. We recently moved into a new house and the house did not have fiber installed, so when we went from the 100 plan to 500 right when they installed it. After the installation, our data usage has been going through the roof (60-150gb a DAY) - I feel like this is almost physically impossible considering none of us actively stream HD all day, we don't use any large cloud services, and our work-from-home situation is exactly the same as our old place and we never even went close to going over our data limit. We had to upgrade to unlimited, but I feel like Cox is miscalculating our data and refuse to check the metering on it. We used to have the panoramic modem given by Cox, but when a guy came over to install Fiber, he took it away and said that there would be a modem installed outside (?), not sure how that works, but I'm almost positive that has to do with our data going over so often. 

Does anyone have any other options for us? Cox has not been helpful to us and I'm not sure if I want to take the time to go to a Cox store to pick up a panoramic modem, pay even more for the $11/month service, and possibly have to pay someone to install this modem because apparently we need a technician to do it? We're highly considering taking the time and effort to switch over to AT&T just because of the frustrations that Cox has given us.