Being charged $100 installation fee

I chose to self install my internet and in that process I spoke with an Xfinity representative that said he couldn’t find my signal online on his end even when everything was looking okay on my end. He told me he was going to schedule to have a technician come out to check and told me the fee would be waived. I called today and the supervisor I spoke with said it’s a valid charge, stating I agreed to it when I didn’t sign anything that states that. This is honestly ridiculous! Definitely would not recommend xfinity.