dishonesty about billing for tech service visit

Comcast shipped incompatible modem/router (without me knowledge) for the internet speed I paid for. So I thought internet issues were from the coax ports from my walls. They sent out a service tech, quickly identified that it was an issue with the modem/router. Internet issue was solved. I was told by the support agent that if the issue was from xfinity equipment (it was: the wrong modem/router that they sent me in the first place), then the $100 service fee would be waived. I confirmed this in-person with the tech and he said the charge would be waived. The charge was not waived, and when I called support after to dispute, they said it was a "valid charge" and even if the tech says on their end that the will waive the fee, on xfinity's side they cannot verify if reason for why the tech waives the fee is valid or not. So the $100 charge will go through.

Comcast is running a scam, shipping incorrect equipment, then charging the customer to fix their own mistake and refusing to waive charges like they initially said they would.