My original Apple ID was associated with an email address that is not valid anymore. I updated my Apple ID to a real valid email. I managed to update it successfully with everything except iCloud on my phone. The App Store, iTunes, and everything else on my phone has the correct ID except iCloud.
When I try to delete my iCloud account from Setting > iCloud > Delete Account, I am asked to enter my password for the old email address, when I do so, I get a reply that the password is wrong. When I try to retrieve it, I am asked for my date of birth, and then told that it is also wrong.
How can I change to my new Apple ID?
Best Answer
One new feature of iOS 7 is an activation lock - and this means that you can't sign out or erase the device without entering the proper password for the account to which your device has been locked.
Towards the bottom of the article, it has a link to use My Apple ID web page to check and reset your password if you have forgotten it.
Presumably, if you can't reset the password, you might need to reach out to Apple directly and see if there is an administrative process such as mailing them proof of purchase or correctly answering questions about past billing events to have them reset the account password.