Xfinity Mobile Charge for returned Device

I bought a phone for my wife through Xfinity and we were trying to transfer her number but it was proving to be really difficult so we returned after a week or so. Xfinity then said the device was returned broken (Grade D) even though it was in perfect condition. We’ve spent the past four months trying to get our money back. During multiple phone calls we have been told that the device actually is in perfect condition and received a grade of A, but we still haven’t gotten our money back yet. We even disputed the charge through our credit card and we still haven’t gotten our money back. Since then I’ve moved and now they say my account is deactivated so they won’t even help me get my almost $800 back. The customer service has been incredibly difficult