Billed early on Xfinity NOW

Hello, I was billed a day early for Xfinity NOW. I had an alert set to cancel my service the day before as I had moved addresses, but my card was charged a day early, renewing services at the old address I no longer live at. I contacted multiple support agents who were unable to help me, telling me my service had been renewed on the 17th when it was still the 16th. I canceled auto pay on the 16th as planned to cancel service, but I had already been charged prematurely. I need a refund, as it is unacceptable to charge me a day early and then say there are no refunds.