data overage

My data usage more than doubled in the month of March and I have no idea why.  It is IMPOSSIBLE to speak with an Xfinity rep to ask for help. I've been on a chat for half an hour and the are switching me from person to person and wasting my time. Is it possible for me to determine what device is responsible for my data usage? We stream Netflix and live TV, and browse the internet on our laptops. No gaming, nothing crazy. How did I use 1500gb??