* First To yours yahoo messenger, from there in messenger menu bar(found at the top of the window), click Messenger, then Preferences. You can also use Ctrl+Shift+P for shortcut.A new Tab Will Open there In the General Category, you will find the button “Edit Mobile Device.†(at bottom) Just click it then a new window should appear in your screen for editing.And you are done.
* As you Click “Edit Mobile Device†It will redirect you to Yahoo mobile service , after reaching in that page click †Delete †buttom ( garbage box ) to delete yours messenger service or Click “Edit†To change Mobile number.