Missold product and poor service

I purchased a 2018 Polo TSI in May from Hatfield VW Braam and was advised to take tyre and rim warranty by Dean Dorasamy. To my surprise, when I tried claiming after having had a tyre damaged and after paying for the tyre out of pocker, the guys at Traffic (Insurance underwriters for the tyre cover) I was advised that I was sold a 15" warranty instead of a 17" tyre warranty which the car came with. At this point the insurance provider offered to either upgrade at a cost to me or I take it up with the dealership. I spoke to Dean and he said there's nothing they can do but cancel the insurance and refund me. From the 9th of December I have been getting the run around with no update or response to my emails from the dealer and the refund has to date not been processed.