Please clarify how can a customer pay bank charges for the store when they want a refund. I've never heard of a such

I bought some goods on Sat 06/08/22. Monday I went back to the store to cancel the purchase and I told them the reason why. I had paid R9810 and they told me that they are going to charge me R350 for their bank charges. I've never heard of a such! I left my bank details but haven't heard from them yet. I called them today 10/08/22 to ask when can I expect the money they said they are going to get back to me and I'm still waiting.