Cashier lying

<p>I went to Northriding Checkers to purchase a calculator and a few other items. I paid for them at the cigarette counter because I had less than 5 items. I made my payment and asked for cash back. I then used the same money to buy a chocolate because I wanted petty cash. When I got home I realised I bought a wrong calculator and that's when I realised I never received a slip for both transactions. I went back to Checkers and informed the cashier who ever bothered to check for the slip but was quickly to rudely tell me that she gave it to me. Please advise on who I can address this issue with.</p>