Using Click to Chat
Whatsapp's Click to Chat feature lets you start a chat with someone without your phone number being saved in your phone's address book.
As long as you know that person's phone number, you can create a link that will allow you to start a chat with them.
When you click on the link, a chat with the person opens automatically.
Click to Chat works both on your phone and on the WhatsApp Web.
Click To Chat was developed using a WhatsApp public API.
The link to the API is: https: //faq.whatsapp.com/en/android/26000030/