Takealot does not honor Sales/Promotion related items

Takealot does not honor their advertised promotions or sales. You make a legitimate purchase and pay in full. Then comes their email or message which states that they do not have stock. At this point, I need to mention that the purchase was made within 15mins of receiving the sales/promotion email. Why do they take your funds and then claim that they don't have stock. BTW going back to the advert after receiving the message from them, the advert shows sufficient stock and but at a higher price. Furthermore I am still waiting for my refund.