Change Apple ID
How do I change my Apple ID? I am getting fishing emails trying to get my password so somebody has the ID.
Receiving phishing emails is no guarantee that somebody knows that you have an iTunes account linked to it, I get them to an email account that's never been linked to iTunes.
If you want to change the primary email address on the account : Change your Apple ID - Apple Support
After changing it (or preferably log out everywhere before updating it, and back in afterwards) : What to do after you change your Apple ID email address or password - Apple Support