damaged leggins

damaged leggings, It had 4 holes on the 1st day of wearing. on Saturday went back to the store to return it but the store manager did not allow me to take the leggins again when i bought it it was on 50% sale in June, she told me to take something worth R250 since the Legging is back to its normal price, she claimed that she will not allow me to take same thing again as my kids 's body will still ruin it again, she even asked my daughter to walk from the till so she can see her body structure and my kids was not happy with that demonstration and felt it was body shamming as she compared my kid to hers saying her kid has same leggins but it will never tear like mine did. I wanna understand why was i not given the same product that i bought why was i instructed to choose something else? im not 1st time buyer in this store and we own many leggins and have never exprienced this.