I pick up a 3 kg bag of apples to the teller to buy

I pick up a 3 kg bag of apples to the teller to buy. The cashier told me that the barcode is not allowing him to scan. The teller go back to the shelf to take and expensive bag of apples to scan it. I ask why is he makes me to buy something expensive than what I selected. He ignored me and continued working. I raised my concern to the manager He also ignored me. I was also requested cash back of R100. The cashier didn't gave Me. I forgot to remind him to give my money due to their attitude