Someone hacked my yahoo account.

hi,shiny here
plz help me to recover my yahoo email account which someone hacked it and moreover he changed all my recovery things like alternate email address,phone number and security questions too.i even sent mail to yahoo customer support about this issue but its no use because the hacker changed my security questions.i again tried through "i forget password" but it says that "you can't reset your password in online" I dont know what it means.downthere I found "why should I wait" and it takes me to customercare support.but I couldn't complete complete more than 3 steps in that customercare support page.i dont know why.i have got all my very very important mails there in that email plzzzzzzzzzz help.its highly important for me.