Plan switch fraud

I experienced fraud from Xfinity, and I can't find any way to report this issue and get the serious attention it deserves.

I received an email back in March telling me my speed had been upgraded to 1 Gbps, but that my current equipment wouldn't support the higher speed, so I would need to buy a new modem (I have my own, not an Xfinity modem). I purchased a new modem ($250), but it wouldn't activate through the Xfinity app. So, I chatted with a support rep to get it activated. He said he needed me to click an SMS link to complete the activation, which I did. However, when I later checked my plan, it was only 800 Mbps, not 1 Gbps. I called back and was told that I switched my plan by clicking the SMS link, and since I was no longer on a "legacy" plan, I would need to pay an extra $10/month for the higher speed! I asked them to switch my plan back or to give me a discount to match my previous price, which I was told wasn't possible. They opened a ticket for a supervisor to call me back, but no one ever did.

The representative changed my plan without my permission and lied to me that I needed to click the link to activate my modem. In fact, the link only changed my plan from a 1 Gbps legacy plan to a "new" 800 Mbps plan for the same price. Why would anyone want to downgrade their service and pay the same price? Especially after I paid $250 for a new modem just for the purpose of getting 1 Gbps speed. No one at Customer Service seems to understand this is a problem. Can anyway here help me? How do I officially rescind my link click to change the plan? How do I report fraudulent behavior of an Xfinity rep?