Exchange

I bought toughees school shoes, size number three, at PEP Down Town Mall in Witbank today. Approximately after two hours I came back to exchange the size, unfortunately I had lost my reciept, but the cashier still recognise me. The store manager refused to the cashier to help me with the exchange. Is it possible for me to be assisted with the exchange, since I do not have money to buy my Son another pair of shoes.