How to change Apple ID email address
Don't change to a new ID - you cannot carry past purchases from one to the other without setting up Family Sharing 

If all you need is to change the address which Apple uses to communicate with you, then that's all you need to do - change that Primary email address.
Your Apple ID itself doesn't have to be your current email address, or even actually an email address at all, once it's set up it's really just a "User Name".

So your Apple ID could be fred.bloggs@abc.com, but your Primary email address could be j.appleseed@xyz.co.nz - &amp; nothing else would need to change.

Here's how to do it…


  
  Sign out of iCloud, the iTunes &amp; App store, FaceTime, Find My Friends, Find My iPhone, and iMessage on each device that uses your
  Apple ID.
  Sign in to your Apple ID account page.
  In the Account section, click Edit > Change Email Address.
  Enter the email address you want to use as your Apple ID. A verification code will be sent to your new email address.
  Enter the verification code from the email into the fields provided and start using your updated Apple ID. Didn't get the email?
  


Source : Apple KB - Change your Apple ID