Not happy with Pick n pay service

I visited pick n pay Trade route Mall 45 minutes ago. I was buying few things. I asked the lady at the till to give me cash back. She told me she doesn't have such amount. She called others as usual they told her they don't have cash. While waiting for her to try other tills. She called the customer behind me. I had to leave the shop without cash. I had to go to the ATM as they took me for granted! I am so disappointed