Billed for phone I don't have

I bought a new phone from Apple to replace my old one. I had to go to an Xfinity store to get the activation and number switch. (unlike ATT, Verizon & TMobile where Apple can take care of the activation) At the Xfinity store, it took forever but they were finally able to get my new phone working with my old number. They said to accomplish this they needed to create a new phone first but that it would be deleted and I'd only be charged for the one phone. Needless to say, I got my bill and I am being charged for this fictitious phone they created with a number that is not and has never been my number as well as the charge for my original number. In other words, I am being charged twice for one phone. The most frustrating part is that I can't actually get a person at Xfinity to explain this all to and to help adjust my bill.