Unusually high data usuage

Recently, I have had a spike in data usage at home.  It's just my son and I, we work different shifts, 2 phones, 2 Alexa's, one tablet.  My son streams YouTube a couple of hours per night after he gets home, and I play a few games on my phone and social networking.  We went from using less than 500 gb per month to close to 1500 gb last month.  One day said we used over 300 gb.  I've asked for help on chat, and they don't know.  They just tell me their equipment isn't wrong.  This is quite frustrating, and starting to get expensive.