Unable to honour our Discovery voucher.

We received vouchers from Discovery as part of their rewards programme. But on numerous occasions we are unable to redeem them. There is always some lame excuse from Kauai to deliver. EG : no wifi or an unknown error on there system. The vouchers expire, resulting in us not able to claim our rewards. The unhelpful manager, Tshepo is of no use, and unable to help or assist in this matter.