Trying to Change my Old Apple ID account to my New Apple ID account; email unavailable
I just made a new Apple ID on my MacBook and I want to change the Apple ID on my phone, as it's a different one. But it seems that I can't sign out of the Apple ID account without losing my iCloud data, but whenever I try to change the email it says "this email address is not available. Choose a different address." This could be because I just made an Apple ID account with it, but I can't figure out how else to add the new Apple ID.
I'm very confused.
iPhone 6