Online accessory voucher claim

I upgraded phone online on December and was awarded an online accessory voucher. Was told I need to use IMEI number to redeem the accessory voucher. Upon claiming I realized I cannot select any item of my choice. Tried to escalate the matter but with no success even with the below link

Hi Mordecai, please escalate the issue by sending an email to *** See link for more info: https://www.vodacom.co.za/vodacom/summer-vouchers