Wrong Installation Fee

I'm 5 year customer with Xfinity and from a tech background. I recently moved, I have my own equipment and i know how to install it but there was no connection to begin with at my apartment.

I call the xfinity and they assigned a tech support on the call, she tried 3 times to connect to the device but it dint (obviously) , then she said they will send a technician to my place (she dint mention any charge in the conversation). Next day the tech arrives and he discovers outside cables box to the rented apartment was never connected. He then connected the cables outside, bam! i have internet(he dint mention any charge either). Both the tech rep were professional and punctual but they never said anything about a charge

2 days later i get a bill with $100 in installation charge lol! for an issue that from xfinity side

My gateway, coaxial cable and the way i installed it were correct but since xfinity wires outside my rented home had an issue they charged me $100, and they are refusing to accept that this was a xfinity side issue not customer side issue

Has this happen to you guys?