Expired jungle oats

I bought jungle oats (Tiger brands)and is having some small blackinsects. Is not for the first time, Last year in November I bought at Shoprite (bouganville)and found the worms, I was unable to go and complain just threw it away. Early this year I bought one at shoprite cash and carry(pretoria west) and I found worms also, I saw it after a week I took it out of the box poured it inside the bucket. This time the black insects I saw them when I was cooking the oats and already threw away the slip and the box. At the shop (shoprite cash and carry pretoria west) they said they cannot help without any slip or the box. All of them the expiry dates on the boxes were still far