What Voda bucks

So vodacom entices us with Voda bucks that you can use to play their daily games to win vouchers. These vouchers are valid for 2 weeks before expiring, but what vodacom doesn't tell you is that they remove/delete your vouchers before they have expired... So in a nut shell, vodacom wants you to spend money on them, you gain Voda bucks & play their "rigged" daily games for nothing... This just seems like a **** to spend money & get nothing on return.