Had a follow up visit because the technician didn't fix the problem the first visit, and got charged $100 for it.

We have been having disconnection issues for a month and eventually was recommended we schedule a technician visit. The technician came to our apartment and did the standard checking procedure to see what's the problem. He identified what he thought was the issue was and "fixed it". It was hard to tell if it was really fixed because the internet was fine when he was testing it in our apartment, but the problem we were having was that it would sporadically disconnect. He left his personal number with us and told us to follow up in case anything happens. Just a day after his visit, the internet started disconnecting again, but we couldn't get a hold of this guy. We had several unsuccessful schedules with xfinity technicians but nobody was showing up. Finally, a week later, the initial technician called us to ask how the internet was. He then said we could schedule again and he could ask xfinity to assign him to our job order. So he came over that day to check things in the building cable box and told us that he did what he could and at this point if the internet still has problems, it might be xfinity's cables' problem with our whole building and no technician could do anything more than what he's already done. He reassured that this won't be charged but now there's a $100 charge on our bill for the visit! The worst thing is that even now, our internet is still having issues. How can you charge for something you didn't even fix, or that nobody could fix?