Write an article based on this "Open WhatsApp Messenger. Tap the ⁝ button in the upper-right corner of your screen. Tap Settings at the bottom of the menu. Tap Account. Tap Privacy. Tap Blocked contacts under the Messaging heading. Tap on the name of the contact you want to unblock. Tap Unblock <Contact Name> in the pop-up."
The WhatsApp icon looks like a green box with a white speech balloon and a telephone icon in it. This is your Menu button, and it will give you options to open a New group, start a New broadcast, open WhatsApp Web, your Starred messages, and Settings.  This option has a key icon next to it. It will open your account settings.  This option will show you the number of contacts you have blocked, and tapping on it will open up a list of all blocked contacts.  This person will now be able to call you and send you messages on WhatsApp.