Vouchers don't work - IT problems

I got a gift voucher a few months ago as a gift and the same week bought something on it. This worked fine.

The voucher still has R501 on it but now I have been told that they "changed their systems" and old vouchers aren't working because of IT problems. I go back once a month to try spend it and I get the same story. Every time they take my number and never call me back.

That money has basically been ******. Poor customer service and dishonest business practice, they should have offered me a refund