In light of the recent massive data leak after the infringement of Yahoo but also according to the our morning publication which states that the company επέτρεπε την αυτοματοποιημένη σάρωση των εισερχόμενων μηνυμάτων ηλεκτρονικού ταχυδρομείου στις Αμερικάνικες services information, there are many who are considering closing their accounts. 
To close your Yahoo account, visit this page, and sign in with your credentials.
Follow the instructions that appear on screen. You will need to re-enter your password as well as a CAPTCHA before you click 'End this account'.
If you've done everything right, you'll receive a confirmation that the account has actually been deleted.
You should know that if you close your account, all your Yahoo services will cease to work, and your personal settings will be deleted.
Of course, before deleting your account, you can download your contacts as a .csv file to import them into the new account you create in the service you choose.
https://help.yahoo.com/kb/SLN22580.html
