Zando/Credit Card voucher/discount not honoured

As a FNB credit card holder, the bank recently emailed me vouchers for the holiday season. On 18 November an email was sent with a 20% discount voucher for any purchase at zando,com from [Email Removed] The voucher clearly states \Discount app**** automatically when paying with your FNB Gold Credit Card"& \""Promotional discount expires 4 December 2015\"" I bought a few items totaling R236 and proceeded to check-out. I paid the full amount on my credit card"