BWH not giving me my money back after Builders Warehouse cancelled the order I placed

I purchased 2 x generators online with Builders Warehouse. They called the next day to say the supplier did not have the items in stock. It has been more than a week and Builders Warehouse has still not processed my credit for R19000.00, Now they want me to send proof of bank account despite me sending my bank details, Then I get told that this is not acceptable. That I need to prove the account used to pay them from. That I cannot get the cash which I obviously do not want in cash anyway. Just a heads up that this same supplier was able to supply the same 2 products via Takealot. So this supplier obviously makes sure they have stock at Takealot but does not offer the same terms to customers of Builders Warehouse. PLEASE may I have my money back