I changed my user name and password in Itunes, when I use my phone or Ipad, it askes for the password for the old username password it says it's invalid. I try to delete the Icloud account but it won't let me- Help

Question

I changed my username and Password in Itunes on my computer. Now when I use my Iphone, Ipad, it asks for the password for the old username. when I type the password for that old user name, it says it's invalid. I figured I needed to delete the old Icloud account from my Iphone and Ipad, but they ask for the old password for the Old username. I type it in and it says invalid. As of now, I can't use Icloud or Itunes on either the Ipad or Iphone.... Help!
<Edited by Host>

Answer 1

If the old ID ("username") is an earlier version of your current ID, temporarily recreate the old ID by going to https://appleid.apple.com, click Manage my Apple ID and sign in with your current iCloud ID.  Click edit next to the primary email account, change it back to your old email address and save the change.  Then edit the name of the account to change it back to your old email address.  You can now use your current password to turn off Find My iDevice, even though it prompts you for the password for your old account ID. Then save any photo stream photos that you wish to keep to your camera roll.  When finished go to Settings>iCloud, tap Delete Account and choose Delete from My iDevice when prompted (your iCloud data will still be in iCloud).  Next, go back to https://appleid.apple.com and change your primary email address and iCloud ID name back to the way it was.  Now you can go to Settings>iCloud and sign in with your current iCloud ID and password.