Billd you can cancel your order any time before itis sent and that is automatic. If it is sent you will not be able to use the automatic cancel. ( on the trackmy order page) but you can decline to accept the item. This is recomend by lazada in their conditions. I have a few times cancelled items with no problems. My rule to myself is I do nt cncel if it is my mistake and it has been sent but that is just my morality, Lazada lets you do so, If you receive the items you can still cancel but have to take photos etc. Refunds if you have paid appear quickly in your wallet and you can either withdraw them or use them for purchases once you have activated your wallet which does need a photocopy of your pasport.
I use lazada extensively and have only had one very short problem with a seller which was very quicky fixed in my favour by lazada (It as really a 50% 50% matter who was right me or the seller.