Unwarranted Early Termination Fee

We cancelled our internet service with a CSR named Lasondra during a phone call on 9/23, in which she told us the service would be cancelled on 9/24 and we were within the 30 day window which we would not be charged the Early Termination Fee. We came to find out the service was not actually disconnected until 10/2, which was apparently outside of the 30 day window, and we are now charged with the $110 Early Termination Fee. After several calls, we cannot get a CSR to address this issue and are extremely frustrated. We plan on visiting our local Xfinity store to complain this weekend if we cannot get the situation addressed. Is there anyone here that can help?