Sold expired product

I went to Caltex Wonderpark,Pretoria to pour petrol on the 23rd of February 2016 at around 18H00. While I was there I decided to enter the Freshstop and get something to drink. I bought 500ml of Mageu ( Cream flavour). The expiry date on the package was 02 March 2016. As I normally do when I purchase a similar product, I opened it and took a sip instantly. To my suprise, the product was rotten. I went back to the store and informed the security guard. We went to the fridge and he opened 3 similar products which were also expired. He called out to the cashiers to inform them of the situation. The cashiers responded that they were aware that the products were expired and he should give me the banana flavour which does not have similar problems. This angered me that the store knew that the products were expired and still kept them inside the fridge. I had to suffer from food poisoning for something that could have been avoided. It's very unprofessional of the store and its staff.