Who do I can l contact about bad techs?

I'm having an issue with my Wi-Fi reaching to certain places in my house. Your Xfinity assistant techs said they can't solve it and sent a tech out. The tech who was just here came in, stood next to the modem, did a speed test, and declared the problem non-existent. He refused to go to the areas of my house that I explicitly said were the trouble areas to perform any tests, all while lecturing me on how WiFi is supposed to work and how I'm getting the speeds I should be getting. He was even wrong about that point as I should be getting twice that amount. Maybe he was trying to say that's what the 6ghz band was capable of? I don't know. He didn't understand the concept of throughput, especially while getting a strong connection. He also implied that traffic steering is handled through my phone (partially true) apparently not realizing that's how the 3 band single SSID is handled on the modem side. He explicitly stated he didn't understand my problem.

He came 1.5 hours early, which I was actually pleasantly surprised about. I ended up having to kick him out. I asked him to send a tech with experience in WiFi, to which he said he was that tech. Obviously not. 

I'm very upset by this. I've been having issues with Xfinity's Internet service for a while, and the "advanced tech" agents are sending me articles on how to open my own ticket without that being requested or even talked about. I've never had this much trouble with Xfinity. The only reason I'm still a customer right now is because I can't get anything else. I'd like to talk to someone about this further if possible.