Lying about exchagnes

I went to the Tekkie Town in Centurion Mall on Monday 30 July 2018 and bought a pair of Adidas (white sole) shoes for my partner for his birthday, before buying the shoes, I confirmed whether he will be able to exchange the shoes should they not fit., I was informed that he would be able to as long as it has not been worn and I confirmed that fitting shoes does not mean they have been worn. After happily taking my R1000 (rounded up) they refused to exchange the pair. I gave the shoes to him last night (01 August 2018) to fit, he put them on walked up and down to see if they fit and said that his heal kept slipping out so he put them back in the box. The Manager claims they have been worn out, which is a blatant lie as it is impossible to wear a shoe out from fitting it, I was there myself so I know it was not warn. I will never support such a dishonest shop again in my life .