This looks like a scam. You should not have responded. Change your PW again.

http://www.apple.com/legal/more-resources/phishing/

If you think your Apple ID has been compromised - Apple Support

Try resetting Safari. Close Safari completely from the app switcher window by double clicking the Home button and swiping up the Safari preview pane until it disappears from the screen. Then go to Settings > Safari > Clear History and Website Data. Then do a forced restart. Hold down the Home and Wake/Sleep buttons at the same time for about 15-20 seconds until the Apple logo appears

Are you being invited to click a link to do something?  This sounds like a scam.

Do Settings > Safari > Clear History & Website Data and see if the prompt stops.

If iCloud asks you for the password to your previous Apple ID - Apple Support

If iCloud asks you for the password to your previous Apple ID

Your iPhone, iPad, or iPod touch might ask for the password to your previous Apple ID when you sign out of iCloud. Follow these steps if you can’t sign out of iCloud because the Apple ID email address shown is one you no longer use…