Unlink super-admin account from Central account to add it to another Sophos Central account

Hello,

We have a productive Sophos Central environment and one of our team members created a Sophos Central free trial account for lab purposes.

Now we need that the email used for the super-admin user in the free-trial environment to be released because we have to add it to our productive account as a super-admin as well, and we get the message:

"Email is already taken for administrative role."

What can we do to achieve this?

Thanks in advance...