Impossible to change cash back banking details

Good day, A lady called me this morning from Discovery Vitality but as it was before 8am and I was driving to work (I cannot use a laptop whilst driving), she reluctantly sent me the link on email. The link goes straight to an error message. I have been able to update my banking details for the Discovery contributions but I can't seem to change the details for the cash back. Seems to me that it is very easy to take contributions but almost impossible to give your clients cash back. Please resolve ASAP as I am in the process of changing bank accounts! Thank you.