for the change your Yahoo! email password without your phone number
1)Tap the Menu icon.
2) and If you are using the Yahoo Mail app then tap Manage Accounts.
3) after that Tap Account info.
4) and Tap Security settings.
5) then you need to Tap Change password.
6) and Tap I would rather change my password.
7) lastly Enter the new password and its confirmation and tap Continue.