Refuse to refund

I bought goods in the store on the 3rd on October 2024 @ springs mall when I got home I realised that the clothes were small and also realised my slip wasn’t in my plastic bag. When I tried returning the goods they refused to refund though I never had the slip. I honestly feel not was not my fault and I mean the purchase is still within the 30 days. I mean they retrieve a customer copy but they still refuse to refund me . The clothes are still in the same packaging with tags . The funny thing is I was helped by the same lady