This is a very simple how-to that REALLY helped me. This is for people that want to change their current apple id email to a different email (that may already be associated to a different apple id but you don’t really use it).
This is extremely useful if you don’t want to have to update all of your payment info. and re-download all your apps, and other associated files.
1. Login to the OTHER Apple Id (the one you want to change to).
2. Change the Apple ID to a different email, then VERIFY it.
3. Wait about 20 mins. for databases to update.
4. Login to your old apple id, and you should be able to change it to the one you want now. VERIFY it.
Hope this helps!