If you place an order with a seller, the seller may cancel your order due to lack of stock or availability of one or all of the products in the order.
In these cases, the amount is never deducted from your account. When you place an order, the amount will be retained in your bank until the seller accepts (in this case IF the amount is charged) or cancels the order (in this case the amount is NOT charged). At the moment the seller cancels your order, the bank automatically receives the order not to discount the amount of your order and therefore the discount is never received, so the transaction was not carried out.
For more information consult your bank.