NO CHANGE ON STAMPS PAYMENT

I went to buy items using Stamps. My Items amounted to R675.97. I had stamps of R680. The manager said they don’t bring back change. I was puzzled because when I buy at checkers I always get my change. They said that R4 can’t be brought back I need to buy something else? How ? That’s my money and I need to have the liberty to buy what ever I want. Such conduct 🚮 I’m really not happy. It’s not the R4 that’s stresses me but the issue of dictating how I send my money and that you don’t provide change with MY MONEY🙆🏼♀️