iCloud has my old Apple ID and is prompting for a password, but I want to put in the new id, I can't because it is grey and there is no edit option. I'm prompted for a password to an account that doesn't exist

iCloud has my old Apple ID and is prompting for a password, but I want to put in the new id, I can't because it is grey and there is no edit option. I'm prompted for a password to an account that doesn't exist. Anyone know what I can do to fix this or why this is happening.? I had no issue putting in my new Apple ID everywhere else, I could sign out of the old and inactive account and then sign back in using my new and proper one. However, after the update to 7.3 it did a whole welcome to yr iPad and a set up thing and it went to set up iCloud and had my old Apple ID in grey where I can't change or edit it, it wants the password, when I put in the old password, it say yr Apple ID is incorrect but yet it won't let me change it??????? Anyone???