Gift Card Expiry

I was gifted a voucher worth R1000.00. I used up R453.00 at the Gateway branch. I asked the cashier many times for the expiry date of this voucher and was assured that this voucher does not expire. I tried to purchase an item a while ago and was told that the amount left on the card had expired. I called the call centre who confirmed this. Had I known that this voucher would expire, I would have made a purchase. Its unfair that the wrong information was given to me and I had lost a generous amount of R547.00. I was also told that gift vouchers should not expire. Or if it does expire, the expiry date should be clearly displayed on the gift card. I want the amount back into my card due to incorrect information given to me.

Thanks Avisha