If you are not able to sign into your Yahoo! account in order to change your password, please contact Yahoo! Customer Care and supply as much detail as possible regarding the problem.
For example, if you think your account was accessed as a result of responding to an unsolicited email asking for your Yahoo! ID and/or password, please include as much information as possible regarding the email you received.
If you believe your password may have been collected from a website that was not Yahoo!, please include the full URL of the web page you saw collecting passwords.
If you entered credit card or bank account numbers as well, you should immediately report this to your financial institutions as well.
For further information pertaining to protecting your account and avoiding password scams, please visit our Security Center.