How to cancel an order that hasn't been shipped?

I ordered the "free" Apple watch but have changed my mind.  It is on backorder and has not been shipped.  Nowhere in the email confirmation does it show how to cancel the order.  The "chat with us" link brings up the Xfinity assistant which was no help and was unable to transfer me to a live agent, maybe because it's Sunday.  Is it possible to cancel an order online? Can I go to the local Xfinity store and get it canceled?