Refused refund

I bought paving material on the 17/06/22 at mica parkrand. I went to the shop on the 21/06/22 to cancel my order and requested my money back as I no longer require the material. They said they will charge me a handling fee of over R2000.00, I refused as the material has not been delivered as yet . What they wanted to charge me was even over 10% as per their return policy. How do you charge me a handling fee for the goods that I have not received or inspected. The store manager clearly indicated that the wont be any refund as I already paid, I must take the goods. I have send them an email for them to explain on which ground will the store not refund me, they have not responded and are still refusing to refund me..