Click the Messenger menu and select Preferences.
Click the "General" category.
Click the "Edit mobile device" button and enter your Yahoo! ID and password to sign in to Yahoo! Mobile.
Under the Other Mobile Devices section, click the trashcan icon to the right of the device.
Click Delete.
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TO DISABLE LOGGING YOU IN TO YOUR MOBILE PHONE WHEN LOGGING OUT OF YAHOO MESSENGER:
On your Yahoo Messenger, click Messenger \ Preferences \ General
The last option....'Signing out of Yahoo Messenger'...UNMARK both boxes...click 'APPLY and OK'
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