changing usernames

changing usernames

I am planning to sign up zoho mail with three users free for yourname.com service.
 
Let's day I sign up three users with some username today. Can I change any username after sometime?
 
 
Example: I signup with three username like Ramesh.P, Suresh.S & Laxmi.V but after three months I want to change
Laxmi.V to Raj.P  Can I do that?
 
Thanks,
Tushar