Disappointing

I'm utterly disappointed with the service I got. I made a booking for my mom's birthday. I called in to find out what voucher plans they have as I want the experience to be a gift. They sent me an email with the booking confirmation and dineplan voucher plan. I bought a R1000 rand voucher as adviced. Yet after eating, I'm told they know nothing about dineplan. Yet, I've got proof on email stipulating by them that I should buy via dineplan. In turn, my mother had to pay the bill out of her own pocket when it was meant to be a gift. Also, I was told they took the reference code and password of the voucher. Why, if you know nothing about dineplan? Beyond disappointed. I feel cheated by this restaurant.