Debit my account while I paid cash

Autostyle, I bought two tyres from them online with the option of collecting from Umhlanga store, when ni got there they told me they don't have them in stock, they told me I should have waited for their notification to come once they tyres are delivered from Johannesburg branch, whereas no one told me I should wait, the online receipt didn't say anything, it showed the payment done and that was it and that automatically meant that I can go collect my merchandise. On the 10 Oct I asked them to refund me, they agreed, I waited 5 days for the money to reflect in my account, instead of having my account been credited, they debited my account for the same amount of R1240, I called to aske why they debited my account they claimed is the bank that debited my, they didn't want to take responsibility whereas the debit transaction reflected their reference number. They sent me document proving that they pay me back, they said I should sent that document to the bank as proof. I did send the documents including the debit card despite fom to fnb from 16 October up until now I still have not get my money back.