Disappointed, to say the least

I received clothes as gifts for my little boy for his first birthday however 3 sets are incorrect sizes. They still have the tags on them but no receipts as the people who gifted it didn't provide one. Truworths refused to exchange for size although it's clear it was bought from their store. Now I'm left with clothes my boy won't even get to wear. It's not like I'm asking for the cash back, I just want to exchange for size.