If you are choosing an overnight shipping method then no cancellation request cannot be made.
If your order is dispatched then you cannot cancel the order.
If you want to cancel the order then you have to place the request within 2 hours of order placement. Refund on such cancellation of orders are mentioned in our refund policy, please refer to it
All the cancellation request shall be sent with a valid reason and the complete order details on support: firstname.lastname@example.org