Refuses to exchange the size when it was given as a gift - swing tag attached and even in their gift bag

I recevied a birthday gift for my baby from Naartjie clothes in a Naartjie gift bag. The tag is still on the item. I went to Naartjie and Truworths in Cresta. Both stores refused to swop the size for me. They informed me that I need to get a hold of the person who bought the gift and ask when it was purchased, at what store and means of payment. They also said the person should have got a gift receipt if it was a gift. I have never had such ridiculous service in my life! The item is from their Store with their branding so what exactly is the problem? No other store gives me such a hassle. Absolutely disappointed and will advise people not to buy gifts from Truworths or any of their stores.