If you will like to remove a domain from your Webready website this can easily be done.
To unassign a domain:
Go to Domains
Locate the website that is linked to the domain, click on the edit button and click Unassign

You can also unassign the domain from within the websites page.
First, go to Websites and locate the website, hover over it and click on Select & Edit Website

Click on the domain name shown for that site

On the popup box, deselect the domain for that website (You can then assign a new domain to the website at this point.)

Click Save
You can then assign the domain to another site if you wish.