Lots of hassle to get a refund

Worse service ever after buying car. Webuycars would greatly service you if there is money to be made. However as soon as I bought my car in cash they started to ghost me or not even process refund for my deposit properly. They said the refund would take 72 hours its been a whole week now. If they dont get their head in the game, I would be force to get an ombudsman involved. They contacted me asking for my bank confirmation letter and statements and proof of payment. How can I prove my payment when I paid through your website. My statements are not out yet and if I ask for them it will be an additional charge, who will pay for it?