Xbox giveaway lie

I recently bought a box of Rice Krispies to enter their xbox giveaway competition and for the second time, there was no code on/in the box to enter. The first time, I sent Kellogg's an email, with photos of the box as evidence that there was no code. They only apologized and sent me a reference code with which I could enter. But now this happened for the second time with no code again. I wonder how many people are you misleading to buy your product to win an xbox, but then there's no code after they opened the box. How can I be sure to get a code when I purchase your product again. Hopefully this wont happen for a third time.