Vodabucks voucher codes not working

Vodabucks Rewards Eskom voucher not working. I bought an Eskom electricity voucher on the Vodacom app. However, following the instructions to dial *120*621# , option one leads to an error screen and does not provide any follow up options.

And I don’t have an option to call them as their lines are automated with no options to speak to a client service rep, and they have also blocked options to call me back.