Charged a $100 "installation fee" for a technician visit, after being told that due to Xfinity's faulty equipment, it would be free.

We were charged a $100 "installation fee" for an in-home technician visit, after being told by both the technician and the customer service agent, who made the original appointment that there would be NO charge if the problem was due to Comcast equipment.  These are the facts: we were having constant issues with our TV cable box and, after several attempts to resolve the issue over the phone, Comcast suggested sending us a new box, which we installed ourselves.  Unfortunately, the new box did not work properly, so Xfinity sent a technician to assess the problem.  We were told that if the issue was with their equipment, there would be no charge for the visit.  The issue was with their equipment, which the technician said was an out of date cable box that should never have been sent.  He removed it, and gave us a new box, which works well, so far.  We would not have needed either the technician or the replacement box, if the original unit sent be Comcast had worked as promised.  When he left, the technician assured us there would be NO charge, as the fault was with Comcast equipment.  And yet... there it is on our bill.  When I called to question it, I spoke with an extremely rude and incompetent agent, who barely spoke English, but kept insisting it was a "valid charge".  I asked to speak with her supervisor, and she at first refused, insisting that the supervisor would tell me the same thing, and then put me on hold for over 20 minutes.  I had an appointment, and as it seemed clear that the agent was never going to connect with her supervisor, I hung up.  This sort of blatant misinformation, false advertising and terrible customer service communication is definitely no way to run a business, or create goodwill among your customers.