Charged for returned iPad new condition

I returned an iPad at Xfinity in brand new condition. It was used for two weeks but wiped clean and perfectly pristine condition. I received it back saying it was badly damaged and they charged me $580. 

Xfinity has no record of it. 

The agents said it shouldn't have happened online and in-store they agree it's in perfect condition and they don't know why they graded it that way. 

Also, I want this added to my ongoing fraud ticket with Xfinity but I don't know how to get that done. The iPad was given to me under predatory sales practices (saying it was "completely free") then charging me for a plan and the device every month. They agreed it was fraudulent and allowed me to cancel the contract and send the iPad back at no cost to me. Now here I am, charged for the whole iPad for no reason at all. This is fraud. 

I have a meeting this week with the store manager to demand my refund. I see this happens a lot. What are the chances of my getting my money back? This caused a huge financial hardship for me. This is a scam and I need advise.