Canceling your Sephora can be done through the app. Simply go to the order listing page and find the "cancel this order" option. Follow the instructions and you should be successful. However, bear in mind that this will only work if your order hasn't yet been shipped from the warehouse. If it's already on your way, you may need to contact customer service. Alternatively, you can wait for it to arrive and then send it back - free of charge - for a full refund.