Franchise store won't honor Samsung voucher because HO takes too long to refund! Tough on you Customer!!

Eastgate Samsung store shocking! After buying a Note 9 this weekend from a cell phone company I took the voucher to the Eastgate Samsung store to redeem the "R500 off a Samsung cover". Long story shortened, the manager flatly refused and said I must go back to mobile provider despite the Samsung website clearly stating that the voucher is redeemable at Samsung as a Samsung promotion. She told me that the Eastgate store is a franchise and they don't want to have to claim from head office because it takes long to egt their money! She was very threatening and unbelievably rude. My child was recording the whole interaction and I will supply this to Samsung at request. What is the point of giving vouchers that cannot be redeemed? Furthermore having staff that is unqualified, rude and threatens a mother in front of her child? Samsung Head Office - I dare you to go to the Eastgate store as a customer and see what your brand represents!!! Where do I go redeem this voucher?