Out of line issue

on Monday the 13th of April i made a purchase and paid by card the transaction went through n the funds were debited from our account but was told it`s out of line and i cannot get the stuff i purchased. I argued that funds were deducted and i was told it will be reversed and i must pay again in order to get the goods. I asked the store upervisor for the slip which shows the error and i was told it`s impossible to print since there`s no network. It`s 3days later now and no reversal was done. I found Shoprite's act being selfish n not caring for their customers needs. It's a total inconvenience and they need to refund me the cash asap. I don' t blame eople who despise Shoprite as now they've let me down since i have been their customer for years. How will this situation be prevented in future? N how am I going to be compensated? I'm so frustrated.