Apple ID email address

See this Apple article: Change your Apple ID

Change your Apple ID - Apple Support (SG)

👉 If you see a message that the email address you want to use isn't available or is already in use, check that you or a family member aren't already using that email address with a different Apple ID. If a family member is using that email address, remove it from their account then try to use it. 

Then why you want to update it?

Have you forgotten your password? -> See this Apple article: If you forgot your Apple ID password

If you forgot your Apple ID password - Apple Support

Then see this Apple article: What to do after you change your Apple ID or password

What to do after you change your Apple ID or password - Apple Support

Try this -> with your work iPhone -> Sign in to your Apple ID account page and edit your Apple ID details.

https://appleid.apple.com

-> change / edit your personal email with your work email.