Coming soon on WhatsApp: Feature to silence calls from unknown numbers, says report
As per the report, the feature will be located within Settings < Privacy.
WhatsApp is bringing an added feature for user privacy, allowing people to mute calls for unknown numbers. This is according to WhatsApp updates tracker WABetaInfo, which further said the feature is available under the latest WhatsApp Beta for Android 2.23.10.7 update, on the Google Play Store.

A screenshot uploaded on WABetaInfo gives more details on this option:

As seen above, the button to silence unknown callers can be found within Settings < Privacy. The silenced calls, however, will be shown in the Calls tab, as well as in the notification centre.
As per WABetaInfo, the tool will reduce the risk of people falling prey to scammers, and also allow you to focus on your work or more important tasks.
Availability
The website noted that the feature, for now, is available only for select beta testers. Before releasing any new ability, the Meta-owned platform tests it real-time with some users; the process is known as beta-testing.
A launch for the wider public, meanwhile. will take place over the coming weeks.