I've changed an email from an end user in the contacts section

eg: oldTest@hotmail.com removed for user TestAccount

new email for testAccount is NewTest@hotmail.com 

TestAccount though can still log into Zoho Help Centre using oldTest@hotmail.com even though this email is no longer associated with them. 

When I do a search in Zoho desk contacts for oldTest@hotmail.com, it says no contacts exist with this email.

testAccount can also not log into Help Centre using newTest@hotmail.com even though this is the email address now associated with their contact card. 

This is an issue for updating email addresses for contacts, especially if they were typed in wrong when the contact submitted the ticket. 

Can someone let me know if there is a fix

thanks