E-Reader for Android Is Registered to the Wrong Account?
Kindle Support, You can deregister the E-Reader reading app from your device or by visiting Manager Your Content and Devices on Amazon.
To deregister the E-Reader reading app, your device must be connected to a wireless or data network. From the Home screen of E-Reader for Android, tap the Menu icon. Tap Settings, and then tap Deregister This Device. Confirm the sign out by selecting Sign Out.
After deregistering, you can register your E-Reader reading app to another Amazon account. Go to Register E-Reader for Android for more information.
Important: When you deregister E-Reader for Android, you are also signing out of other Amazon apps with Single Sign On enabled (such as Amazon MP3) installed on your device. After you register E-Reader for Android, you will sign in to these apps again.