Opens on the Samsung Galaxy S6 "WhatsApp" and then typed into the chat Overview top right at the three-point symbol. In the opening menu navigates further on "Settings" and then:
Account -> Privacy -> Blocked Contacts
About the icon at the top right, you can now add a contact to the blocked list. Select a contact from your list. This is now set to the CRL of WhatsApp, which means that you will receive no more messages from this.