Customer has convenience to cancel an order place through several methods. For example if customer has ordered a product and paid for the same online through payment gateway then, customer can mail us at firstname.lastname@example.org with your order number.
If customer has participated in Express delivery (Delivery In Just 4 Hours) then customer has to call our customer care services and place a request for cancellation of order within next 4 hours (For Example if customer has placed order at 1pm in afternoon then he has to cancel order before 5pm because after that cancellation of the order will not be possible as in express delivery, we process orders within 4 hours and ship them).
As mentioned in express service of 4 hours delivery, process for packing and delivery starts as soon as the orders are placed for best service. So sometimes it is not possible for us to cancel the order if the delivery van is in customer's residential area, so such a orders are fulfilled and can not be cancelled.