Unusually High Internet usage and Overage charges.

I have 2 TV's that stream, other than that there is not a lot else connecting to the internet. I have a $159.00 for 1.2T that apparently due to overage charges is now more than $500.00 for a one month usage. I am more than ready to find another service provider that doesn't gouge it's customers. We pay the bill every month, there is no excuse to be charging overages for more than $340.00.