UNFAIR COMPETITION ENTRY'S

Yesterday I went and bought your Power Play special for two tins for R30.00 at the Total Garage in Kempton Park. Due to R50000 that can be won. I tried yesterday to enter you competition where as you dial *120*5010# and follow the prompts. The funny thing is, Yesterday when I tried to enter my code from both Power Play Cans. It said that the code is invalid or already used. I retyped the code many times but still got the same response. First I didn't think much about it, but this morning a bought another special at the same garage and then I got exactly the return message. How do you expect customers like me to enter the competition if someone else already used my codes from both cans. I am sitting with the slip and codes in front of me, I am not saying that I would win the competition I am just saying that you don't give the public a fair chance to win the competition. Doesn't each individual Power Play can have its own unique code? How could someone else use my entry into the competition? This is really unfair? If you can just please explain to me how this works because if all the cans out there has the same entry code I really don't want to participate or buy your product.