Unsatisfactory service & unfair loss of cashback.

Clicks Maclean in King Williams Town ?????????? I went to buy sunscreen, the boxes were empty and I understand it’s due to theft probably. I paid at the till and used my cash back . When I was walking out, I realised it’s not the correct sunscreen and I went back inside. They wanted me to pay more money and I lost my cashback just like that. They could not do a return and factor in my cashback. They instead wanted me to pay full price for the correct sunscreen. When they were first confused as to how much I should pay. I’m so disappointed! If they have empty boxes, they should first check with the customer if it’s the correct item before the sale.