Unfair returns practices

My partner received a clothing set from YDE as a gift on his birthday , the person that bought him the gift did not give us the receipt as they thought the sizes and fit would be perfect for him , on Tuesday afternoon , my partner went to the Mall of Africa branch to exchange the items for something else and they insisted on the receipt . The tags are still in place and the items have never been worn and they refused to exchange them, please advise on what we then need to do with these items, the person that bought this no longer has the receipt . Do you ask customers if they would like to have gift receipts upon all purchases as this would curb the problem we are currently facing