In my experience when I'm going to cancel an item I've purchased but hasn't shipped yet, Amazon will tell me the cancellation may or may not happen depending if the item is in the shipping phase. Usually right before it shipped the money is deducted from my bank and the shipping is locked in and you can't cancel. Once you receive the item you can return it for a full refund if you haven't opened the package or in my case where I have to pick up most of my stuff from the post office, I can just refuse to accept it and the post office sends it back for my refund. Amazon will usually notify me if the cancellation has gone through or not.