Bulk account, charged money for installation even though received a defective router

I'm in an apartment complex on a bulk account. I was originally assigned to one unit and picked up my gateway, then was reassigned to a different unit before move-in. I called Xfinity beforehand and was told the original account had been closed and everything transferred. When I moved in and plugged the gateway in, it blinked white and never connected. After several hours on support chat across multiple days, a technician was dispatched and came 5 days later. He replaced the gateway. The underlying issue appears to have been that the original account was never actually closed, so the equipment was still keyed to the wrong unit.

A month later, with no prior notice, I was billed a $100 professional installation fee. I was never told at any point that the visit would incur a charge. Given that this was not a failed self-installation I'm requesting the fee be reversed.  Separately, the original unit's account still appears to be open despite multiple requests to close it, and I'd like that resolved too. Thank you!