"Installation Fees"

I just got an email with my latest bill and it is $100 higher than it should be for an "Installation Fee."  I installed my router and modem myself but a technician came out to repair wiring outside of my home. An Xfinity customer service agent made the appointment for me over the phone and did not mention the charge - in fact, she said that my account would be CREDITED for the time that I spent without internet service. I did the installation myself and am not responsible for the Xfinity lines outside of my home so why am I being charged?