Once you have approved an order, there is still a chance to edit or cancel the order, but only before it is taken into production. You can cancel the order via All Orders in the left-hand navigation of your SPOD App. You can also change the shipping address before an order moves to In Production status.
Once an order moves to In Production there is no longer an option to edit the details of the order or cancel it. SPOD will not refund orders that need to have details changed, or be canceled.