Exceeding Internet Data Usage

A few days ago, I received a notice from X-Finity that I had used up 90% of my monthly Internet data already.  Apparently, I am allowed 1.2 TB. This doesn’t make any sense that I would have used that much this month, as my Internet and streaming habits have not changed in years, and the most data I’ve ever used was in the 600 GB range last December.  I tried calling customer support, but they said there is nothing they can do unless, and until, I go over the 1.2 TB limit, which, I now have three days later.  I haven’t played online games in years, and, even when I did, I still did not come close to going over my limit.  Something is obviously wrong on X-finity’s end.  There was a tech person that came to my house a few weeks ago to replace a part on a cable line that was damaged from a lawn mower, so I don’t if that has anything to do with it or if their system is just reading my data usage incorrectly.  Either way, X-finity needs to correct this.