Unreliable loyalty programme

Pick n pay smart shopper leaves a lot to be desired it attracts customers to their stores and the vouchers are not worth a cent yesterday i went to a family owned store in the helderberg area when i presented my card i was told tgeir was no dicount on the card despite the discount showing on my app i was then told to print a voucher from the kiosk which still not did not work after 45 minutes with management who made phone calls to supposedly head office I was tol the voucher was only for 340ml cans unfortunately this product only comes in 340ml bottle or 330ml can management were not aware .what is the use of a voucher in black and white or the voucher on the app if it cannot be used this is the second time this has happened and never any feedback from management. Now I use checkers where I dont have to waste time with a loyalty system that only works ehen it wants too