Its Illigal to have a expiry date on a Sunglass hut voucher

My wife and I bought 2 x pairs of shades from Sunglass hut in 2017 for R6880.00, Yes I know, 2017. We received a gift voucher to the value of R1356, which I misplaced. 2020 Finally found it and went to purchase a pair of shades, only to find out that there was a zero balance on the card. Apparently Sunglass Hut reduced the value a year later. It is ******* to have a expirey date on a voucher.

I would like my gift card reinstated and an additonal gift card for the embarrassment of going to the shop with a zero balance card.