How do I change iOS settings to "not" sync notes over the air with iCloud
If you are being returned the following iTunes message (see screenshot below). Make sure to only have a single notes account called "On My iphone". You can access your iPhone notes account by opening the Notes app on your iPhone and tapping on "Accounts".

You can bring all of your iCloud notes to your "On My iPhone" account as per these directions: How to transfer iCloud notes to "On My iPhone" account