Double Billed

I was on the phone with an agent from comcast and it was taking forever for them to process my payment so I decided to log in online and make my payment there. After I make my online payment the phone agent says OK I got your payment processed sir! and I was double billed. My bank can't cancel the payment because it's not technically fraud and Comcast is saying they wont give me a refund? What can I do? VERY FRUSTRATING as if i was to wait the refund isn't credited until my next month's bill is due and it's given as a credit. I am remarkably mad