Xfinity is a cheater [changed the plan and increase the price without my permission]!!!

I have been using xfinity for about two years. In Aug 2022, because the first-year contract ended, I chose another plan (600Mbps plan, original monthly fee is $60) and agent provided $20 discount by moving one of my phone line from AT&T to xfinity, so the final price is $40 per month.  In Sep, I was charged about $40 and then xfinity overcharged me with $50 in Oct. I found this change and argued with the xfinity agent and the agent committed to change $50 per-month fee into $40 per-month fee. Then in Nov, I was charged $40.  But for Dec 2022 and Jan 2023, xfinity overcharged me again!

I contacted the agent, the agent changed the statement and said I updated the plan into the 800Mbps plan and the original price is $70! But  I am 100% sure that when I discussed with agent in Aug about the plan, they say the plan is 600Mbps and original price is $60. This is really ridiculous and disgusting! This makes me feel xfinity is totally a cheater!

 By searching on google, I noticed that many customers said xfinity changed the plan without the user authorization. I would urge xfinity to provide the conversation history in Aug and follow the contract.