Expired Yoghurt

As I was doing my weekly shopping I bought yoghurt. When I got home, time for dessert to my surprise the yoghurt was sour and clotty. I work 8 to 5 I had to take it after work the following day. When I got there around past 6 and explained my situation I just got dismissed by the staff who also gave me an attitude. On the yoghurt itself it says expiry date is February 2016 but inside it has already expired or maybe it was not refrigerated. Bloed mall spar sells expired food and the staff do not know how to communicate with the customers. They need to learn customer service. How to satisfy their clients. I just left that yoghurt at their counter and walked away