Mango: Vlieg in jou moer

My wife and I booked tickets from Cape Town to Port Elizabeth last year. But due to COVID, the flights were cancelled and we received vouchers. Great stuff up to here. We then had to fly to Bloemfontein this year, and used the vouchers. The flights were a lot less cheaper, and we had a substantial balance left on our vouchers. When we tried to book flights to Johannesburg, we were informed that we forfeited the balance of our voucher. This is *******!!! This matter will be escalated