Maggots in maize meal

On the 19th of February, I bought white star maize meal at Checkers in Springs Mall, only to get home and find maggots inside. I took it back to Checkers in Carnival mall because that is close to where I stay, I opted for super sun instead, when I got home, I found the same problem. When I took it back again, checkers helped me to phone Pioneer foods to explain the problem. They promised to send me a voucher as consolation for all the trouble, but the voucher never reached me up to this day. Yesterday I phoned to enquire, they told me to go and take a photo of the product, which I obviously no longer have with me. I did send them photos before, but clearly those were not enough for them. I am disgusted at this poor customer service and am even afraid to go back and buy maize meal from them.