Cannot refund order before it has been received!!???

I've ordered accessories for my new apple watch I've bought last week (4/3) at Takealot which is I quite need urgently for some reasons, but Takealot could only deliver the 16/4. Miraculously this morning it shows they will deliver this morning with the message "order not yet shipped" which I can guarantee you it will not be delivered tomorrow. So, yesterday I've bought all the accessories at my nearby supplier because I only receive it the 16/4. I've read last week on Takealot's website that you can't cancel an order once it's been made!!?? Why not?? Only when you received the parcel you can return it!?? What is the difference? It will cost Takelot much less money to ship the parcel and collect the parcel than to cancel it from the get go. I'm unsatisfied that I can't cancel my order, because now I have to wait for this order to be delivered and have to return it as is without opening the box and as for a full refund!! This is totally unnecessary!! Will you please look into my order and see if you can cancel it before it's been shipped?