Bad customer service

Hi my name is Refiloe and I am residing in Kempton Park. I bought some snacks last week and before opening them I realized they were 2 months expired. I took them to the store and all I got was a refund and free pack, my shock was that the expired stock was still in the shelves. The branch manager then told me "sorry ma'am" which I find to be a lousy apology. He said those involved will get written warnings but is that enough for a customer who has experienced bad service before with the same store??? I have pics of the snacks an receipt. Mind you I'm heavily pregnant and had to go back to complain. How do I know the process will be followed and is it really fair to be getting such service from a big store???