100% Mistery Discount Scratch and Win

I am absolutely ****ed off at my experience at Jet Store in Centurion .My wife approached the cashier to pay for 2 items, and she asked me if she has a Jet cash Card and she said no, then she asked if we would like one because we will get a discount if we scratch this voucher, so she entered my wife's name and number on the system and swiped the cash card, then she gave my wife a stack of vouchers and asked her to choose one, she chose one and scratch it, she looked at the voucher number and said oh my God ... this card is 100% off all items .. You see this number .....51 in the end it means 100% off, then she told me go get more items u will get them for free... that's when we took more items and went to her.She even left her till Point and came to us in the store and called us and she was pulling our trolley in the store and assisting us to the cashier.(This can be seen on your camera's in store) and then she entered the items in the system and then swipe the jet cash card and scan voucher and then she calls the admin supervisor and shows her the computer screen and they pull the screen away so my wife doesnt see. My typing characters are finished and cannot continue this complai