Complaint against pick n pay mahube mamelodi

My name is Sinky Betha on the 19th of April 2018 i bought a 12.5 kg of pick n pay maize meal. We coocked the maize meal on the 19th and on the 20th only to find out it was infested with worms and flies . I took it back to pick n pay and i was told by the manager by the name of Eazy that its not their fault. Its a supplier's fault so there is nothing he can do rather than giving me refund or exchange. He did not even bother to apologise or to show remorse. My children had a stomach ache and i gave them allergex medicine. I since logged a complaint with them and i was called by their food doctor saying she spoke to the store owner and they are willing to give me another maize meal for free. I feel highly insulted and i need an advice on how to take this further. ********** 355 please help my email address is **********