Removing old Apple ID
Searching for "change apple id appstore iphone" I stumbled into this page which shows how to do this on an iPhone.



Once you've signed out you can either sign in or create a new Apple ID.


  
  Log in to another Apple account that already exists by entering the appropriate login details at that screen, OR
  Create a new Apple ID by tapping on the “Create New Apple ID” button, which automatically logs in with the new Apple ID when
  finished
  


References


How to Change the Apple ID on iPhone, iPad, &amp; iPod Touch