Despite its feature-rich nature, WhatsApp still lacks a straightforward way to communicate with unsaved contacts. However, reports suggest that WhatsApp is working on introducing this feature in the near future.
The beta version 2.22.8.11 of WhatsApp on Android reveals that the company is developing a method for users to easily connect with unsaved contacts. The design shows that simply tapping on an unsaved number within a chat bubble will present several options, one of which will allow you to call that specific number immediately. Other options that appear upon clicking the unsaved number include "Request" and "Add to Contacts."
One major limitation of this option is that it will only work with numbers present in a chat that you can click on. This means that someone else must send you that number, or you need to send it to someone before you can tap on it to access the new options.
The feature is still in testing, and it will take some time before users can see it in the stable version of the app. Until then, the only way to start a conversation with an unsaved contact is to open a browser on your phone and visit the URL https://wa.me/phonenumber, where "phonenumber" can be replaced with the number you want to message, as reported by the Indian Express.