Charged for Undelivered iPhone

So, like many people, I bought an iPhone 12 mini from Xfinity when they came out in November (2020). The problem is, Xfinity never actually delivered the phone to me and yet continues to bill me for a device that I have not received!

A little background:

I ordered an iPhone 12 mini which was supposed to be delivered on Nov. 18. The phone however never arrived. The shipper, FedEx, continually lists the package as "on FedEx vehicle for delivery"  but starting on the 19th tracking indicates that the "delivery date in unknown." I've contacted FedEx over five times and they clearly have no idea where the package is. One of their reps eventually advised me to contact the seller, which is Xfinity.

It's now Dec. 10th, *22* days after the package should have been delivered, and I've called Xfinity over 10 times about this matter (since Nov. 20th). Every time I call Xfinity, I'm told that they can't assist me or that I need to wait an undisclosed amount of time for them to review the issue. I've been transferred and put on hold for hours at a time and I've even been hung up on a couple of times. One Xfinity rep assured me that she had spoken with FedEx and that the package would be delivered "the next day" even though the "next day" was Thanksgiving (surprise, nothing arrived). 

How do I go about getting a replacement device shipped to me or a refund for the charges that have already hit my account? At this point in time I'm seriously considering getting my bank involved for fradualent charges. Any advice would be greatly appreciated.