Buildersmate is spot on.
If the item was sold to you defective, or not fit for purpose as described by the shop/salesman then you are entititled to a reasonablke replacement. If a replacement is not available, or not suitable for other reasons (eg multiple returns on item, size not available) then a refund will be given.
If the item was bought then you changed your mind, realised the description you gave was wrong, decided you couldn't afford it the the store is under no obligation to do anything.
Some places will let you get refunds on noddy reasons, but that is store policy NOT LAW!!