Unfair consumer practice by Adidas South Africa

Purchased running shoes a the Adidas sample sale on 1 June 2019. At the sale, customers were informed that they were not allowed to try on the shoes for fit. I purchased the shoes as I generally am sample size, but when I got home, I found the shoes to be too small. My efforts to return the shoes for a different size, or for a different product of the same value was declined. The advert for the sale did state that refunds or exchanges would not be allowed, but this is surely unfair, given that the consumer was not allowed to try on the item to be purchased first?