Pests in Food

I bought a bag of Inyala Maize Meal on Friday, 1st March at Makro Springfield. I used it 3 days later and found it to be full of pests, it was still sealed so i couldn't understand how they go there. I checked all my other food i.e. flour, sugar etc but none of them had pests which means this maize meal came from Makro with the pests which is very disappointing.