Changing the domain of a user

When creating an Office 365 account for new employees and you mistakenly use @breeneng.com or @bei-servicesinc.com and want to change it, follow this guide.

1. Login to Office online and go to Admin page
2. Go to active users and click on the user account you want to modify
3. Click on edit in the Username / Email            (step 2-3)          
4. Add the username and then from the drop down choose the desired domain (either @breeneng.com or @bei-servicesinc.com) then click +Add and then save.
5. Do step 3 again, you should now see the alias created, set it as primary.        (step 4-5)