I'm looking for the answer

I cut the cable and just use Xfinity for the internet. I had no issues with Xfinity and no problem with my usage until someone at Xfinity came up with an idea to earn more revenue because everybody is cutting cable.   Then a few years later Xfinity started texting me that I was nearing my limit on internet usage for the month. I was never informed about a limit for internet usage. It was unlimited.  Now they are limiting my use of the internet. They said they were going to charge me for it. I thought it was a scam. My original bill was $49, then it went to $79 bill. Now it is $99. What the heck? I tried calling but they don't let you talk to people anymore. Now you have to chat with them. I was told that my old modem was the problem. I said it works fine but they said for my 400Mbps plan it did not work efficiently.  They said I needed to upgrade to one of their modems for a monthly fee of course. I asked if I could by my own modem and they said "no" I had to rent their modem or I would have to pay extra. Looking into ATT or Verizon now.