How to change account email (old panel)?

Hi, I need to change my account’s email to deliver my project to the client.
I read somewhere and faqs that i can change this, but with the old panel, there is no luck.
I tried to find the helpdesk contact about this, but also no luck.

I saw that some of the user have already used the new panel few weeks ago, but mine was not migrated yet, and i need to deliver this in 2 weeks.

Anyone know how to do this? while keeping the credential of my database/file manager.

Any idea will be appreciated!

Change your email is easy on the new panel on the old panel not possible.