How do you change that from My Orcon ?

When i joined i called cust service and told them to change my main email to @slingshot.co.nz

But since then slingshot closed my account and i've switched back to Orcon and just now I remember that I have to change my main email back to @orcon  for the online invoice to be sent to my inbox.

But i can't find the option on my orcon. I see the email address on the account home page, but when clicking on it only opens outlook , cant find option to change it.

Or do i have to call them ?