Kept getting charged after disconnecting with rep on phone call.

Good evening, I recently cancelled my service due to moving into a new home in a different city that does not have Xfinity available. I've been disconnected for about a month and had already switched to another provider for the remaining tenant. Somehow I got charged for the current month. Please help me resolve this because it feels odd paying for a service I was certain I cancelled and haven't even used for a month at this point. Thank you!