Expired product

On the 1st September I went to checkers springs mall to buy groceries. Amongs the items the eas bokomo nature source from pioneer foods.my child ate it then it was about to be finished then on the 8th we went ti the some store ro buy another one.On Monday my child was about to finish the remaining one she was reading the pack when she discovered that it was expired on thr28.05.18.The. PD was 28 08 17.then when we were checking the close pack PD was 26 03 18 BB was 26.12.18 .we were confused about the life span of the product one take year to expire one take months in same year.I toik it back to cherkers I spoke to the manager I didn't have slip but she was able to print the slip because I was using card to purchase. I ask her about the different life span of the same product. She said its not their products I can phone Pioneer food to find out.My concern is expired product was found in the shelves worse my child ate it.Big store like cherkers can keep expired products in tbe shelve. Worse it was consumed by my child. Neglegence on the park of the store . irrespective of life span from pioneer products product was bought at cherkers.She refunded me .but I was not happy at all my time was wasted .petrol .taking product back to the store.