Ster Kinekor discount - not really!!!!!!!

I booked a cinema ticket with my discovery vitality ster kinekor number - i then proceeded to check out and thought that the price was a little high - but paid anyway as I had entered my number - thinking that that was the discounted price! well it wasn't and your call centre said that i should have called them first! WHY did I have to apply my number?????? My thoughts were I app**** my discount card number and that surely should have got me my Discovery Discount. SHAME ON YOU DISCOVERY VITALITY - that has really left a bad taste!