Poor quality insoles trainer shoes

Poor quality insoles trainer shoes. My son bought trainers and around 3months of wearing them the trainers insoles got worn out and the trainer heels are left opened hurting my son and made him too uncomfortable. He watsaped Mr Price to complain and request for refund and Mr Price requested for proof of payment and unfortunately he didn't kept the receipt but had proof of payment through bank transaction. Yesterday he went to the store where he bought the trainer shoes they informed him that since he did not purchased the trainer shoes with the account Mr price is not in position to issue him with the copy of the receipt. Mr Price showed no interest of helping customers who do not have accounts in the same way they treat their account customers. I have found that not acceptable because in their records they have all transactions of sales of accounts and cash so they must retrieve the cash sales receipt same as they do with account. I need fairness and appreciation from Mr price and also for Mr price to look for the receipt so that my son can be able to return those trainers. My son can't loose his money and Mr price and the shoe supplier benefited from him