I have a client user which has the correct email address, but the name has been populated incorrectly.

How do I change the name of that user and where?

I have deactivated the user, and deleted the deactivated user, but when I try to add the user again, using the email address which is correct, it automatically picks up the incorrect name of the client user I supposedly deleted.

How do I fix this?  If I have to deleted the user from the organization - where do I go to do this, and how do I do this?  I need to assign the client user to project tasks, with the correct name against the email address that is already sitting somewhere in Zoho.