Inadequate Staff - Selling wrong spares

I came in early in the morning of the 27th April 2024. I humbly requested a set of mud flaps for a VW Polo Vivo 2019. I got home to fit them in, the front set fitted in front but the back didn’t. I returned back to Goldwagen Montana and they refused to exchange or refund me my money. I explained that nothing is damaged, their bolting isn’t damaged or packaging damaged. They refused until I said to seek for Legal Advice from my lawyer.