Confusion about bill

I had a problem with my internet and since I couldn’t resolve it on my own, I went onto the website and was offered to have someone come over and check it out. Nowhere on the website did it mention that it would cost $100, nor did the man who arrived to “fix” my problem. When the man arrived, all he did was walk in, told me that that tv was just old and I had to buy a new one, and left. He did absolutely nothing yet I was still charged $100 even though he was only here for a minute? I am just confused because I’ve been a customer at Xfinity for the past five years and they have never done anything like this? Why was I charged so much even though no price was listed nor was the guy any help?