Billing

I purchased stuff on Sunday morning which came to round r50 so I pay with my card few minutes later the cashier tells me that it's been declined so I pay cash later on that day I logged on to my bank account and see that the transaction did go off when I spoke to the manager she says there no record to pick it up and that I should come there with a bank statement which is non sense I'm not going to pay another r50 for a bank statement due to the cashier mistake I want this sorted and I want my money.