Johnny Walker Whiskey South Africa 200th Anniversary Competition Useless Vouchers

Johnny Walker South Africa ran a competition to celebrate their 200th anniversary and entrants could #win R 100 vouchers. I entered and won a Superbalist voucher. The voucher number is not accepted by Superbalist. I've emailed and Facebook messaged Johnny Walker many times over the past two months with no response. Now I've gone public on their twitter feed. I know it's only R 100 but it's really shoddy service on their part.