PnA mall of africa Bad client services

Went to PNA Mall of africa few days back ,upon arrival to the till point I realized I didn't have my card asked if I can use scan to pay method and the cashier allowed, after payment I was told I cannot take home my goods because it's pending and money had already left my account...was told to make another payment so I can keep my stuff and the other will reverse till today it hasn't...such an inconvenience,why was I alowed to use the payment method if they knew it gives them problems