Unfair exchange Policy at ZARA Stores in Sandton City

I bought clothes for my children at ZARA stores in Sandton City. Clothes did not fit, I went there the following day, clothes still with tags on and they refused to EXCHANGE them because I had lost the till slip. I spoke to the store manager Riccardo and he told me about "the store policy". Complete ******* especially around children's clothing. I am never buying my children clothes from them again. And I will not recommend ZARA kids section to anyone.