WhatsApp Help Center - How to delete your account
How to delete your account - You can delete your account from within WhatsApp. Deleting your account is an irreversible process, which we can't revert even if you perform it by accident. To delete your account Open WhatsApp. Tap More options > Settings > Account > Delete my account.
Tap More options > Settings > Account > Delete my account. Enter your phone ... Your information shared with other Facebook Companies will also be deleted.