Woolworth vouchers not working

Sad experience at Woolworth Bryan Park shopping Centre Johannesburg yesterday. I received a gift voucher on my Woolworth mobile app for a R10 discount on cakes if I buy over R100?, so I bought for mothers day a chocolate cake and at the till I was told by the very friendly cashier Gudani Masisha there is a problem since yesterday already, that the tills will not register the voucher, I ask for the supervisor which caould nothelp me, then ask for the manageress, Joyce Nanguane? and ask her to manually override this, as my voucher has not expiered, and is still valid, she also said she cant help me... I was not a happy client, and told her that I will lay a complaint, since we spend a lot of money with Woolworth and for such a big company not having a way to manually override a malfunctioning till system is just not good enough for me. Please Woolworth update your systems, that's very poor service!