Filing a complaint

How do I go about filing a complaint on the representative I just spoke to from the loyalty department? We were on the phone for about an hour and a half and the entire time he was gaslighting me and lying about the costs and details of the plans just to back me in a corner and force me into switching to a plan that would give me less but cost me more. Saying that I had to just trust him because he talked to a tech guy there to confirm I wouldn’t notice the much lower speed difference of a new plan because the service has been upgraded and since my bill went up after the discounts dropped off that I had no choice either way I’d be paying more if I don’t change my plan. He lied to me about the prices because he kept only telling me the price that would be if I used autopay and paperless and didn’t mention that detail until I asked. The tone and his choice of words the whole time was gaslighting and disgusting, after being a customer 13 years my plan is grandfathered in so why is it just now my discounts dropped off, oh I know because xfinity wants to force me to switch and pay more either way. After that call and how rude he was I will be switching to another internet provider now, it’s bad enough the new customers get all the deals and discounts but a loyal long time customers get nothing but ripped off while receiving spotty service that doesn’t deliver what was promised. I’m so over it but that guy needs to be reprimanded and retrained most of all.