Charged installation fee $100 when we were told by both agent and technician that it would be of no charge

Setting up new internet at a new place knowing Xfinity service worked here previously. We had 3 people in the IT fields setting up the modem at different locations of the house. After many attempts we had to call technical support. Tech support asked us to try a few more things, still didn't work... so he decided to send someone else letting us know it will be of no charge since we tried everything and it would not be our fault. Tech came out next day and verified internet wasn't working. He eventually had to go outside and do some quick work (not sure what) and came back inside to reset things, which at this point worked. He also informed us there would be no cost because whatever he did outside was necessary for internet to work. Fast forward 2 months, we see the installation charge of $100 on the 2nd bill! Called Xfinity and were told this is a valid charge because we said we would do a self-install and couldn't so they had to send someone out. How is this good customer service when the solution to the issue was out of the customer's control? Seems like this happened a lot to other customers and apparently whenever they send a someone out with a truck to you will get charged, no matter if it's your fault or not. Terrible system and customer service whose favorite phrase is "valid charge". Can't wait to switch service and strongly not recommend to friends and family. Glad I'm in the area where Xfinity is not the only internet option.