Damage school bag

I am disappointed January i bought the bag a day before the school reopen.on the 9 the child came home crying said to me the bag is damaged.a new bag damage the old one still in good condition.the zip damage n the belt torned.when i went to the shop the sales man told me the bag can be exchanged they need prove and i used my card to pay for the bag. He said it doesnt matter without tje slip they cant help me even though the purchased is showing on my bank statement.now m sitting with a bag that they promised me that is a good quality bag.but the belt is torn, zips out

I don't want money i just to be exchanged .now my child is using a plastic bag to carry her school to books.its not even a month the bag its damaged.a bag from total sports still good n its three years