Being Double Billed for a Second Account for two months

I started Xfinity service this January, I selected self-installation and received the Xfinity Gateway shortly after. The installation wasn't smooth and so I went to one of the stores looking for help. The store sales helped resolve the issue. The service was set up and I was able to use the internet with out an issue. But what I didn't know is that the store sales fixed the issue by setting up a SECOND account, which I only realized after more than a month when seeing I was double charged in my checking account for two months and I already auto-paid both!

I called custormer service. The rep said I need to go to the store to fix it. I went to the store and they helped me cancelled the second account but when I asked about the refund, they said it's not something they can fix in store. I've spoken to customer service on the phone about this several times and I have yet to get any kind of resolution. This is rediculous.

I have ONE modem, at ONE address, and my service is paid for and up-to-date for that account. The customer-service representatives have confirmed this to me. Why am I being charged again for a separate account in my name, for which no service has actually been rendered?