Unfair practices

BP and Pick and pick n pay are currently running a competition that you can collect a car after you have made a payment of 2400. But now some of the codes that i claim with decline and when i called them to enquire they tell me that there is a limit of 4 swipes per smart shopper card. But they not willing to address the issue of the declined codes. So what's the point of running an unfair campaign because this is not a competettion