The trader shall ensure that the consumer, when placing his order, explicitly acknowledges that the order implies an obligation to pay. If placing an order entails activating a button or a similar function, the button or similar function shall be labelled in an easily legible manner only with the words ‘order with obligation to pay’ or a corresponding unambiguous formulation indicating that placing the order entails an obligation to pay the trader. If the trader has not complied with this subparagraph, the consumer shall not be bound by the contract or order.