[e-mail] to [e-mail]

How do I change the extension of my e-mail address

[Philon]

When filling the registration form for yahoo mail I didnt realise that my e-mail address would be [e-mail] until it was completed. It wasnt shown like this at all.

I want my e-mail address as [e-mail]. But there seems no way to change it. Unfortunately I have used my real name as my yahoo ID and cant just create a new account cuz I want to remain this ID.

Is there a way to change the extension or to cancel this account?