It's called "3rd party accounts visibility".If you read the article at the link I mentioned above, and scroll down and read the comments section, you will find the exact steps to access it and turn it on for WhatsApp, which will fix the integration a...

There appears to be a hidden option (Thank you Samsung!!!) to control "3rd party accounts visibility" in the Samsung Contacts application. This can be accessed like described in the comments at this link - credit to the original posters : https://www...