You can set a condition in your flow based on validating the lead's WhatsApp number.
To do this, go to Automation Flows,
And by clicking "Open Builder, add a block of "Condition" and select "Does the lead have a phone? - Yes, and it's a valid WhatsApp".
From there, customize the flow according to your needs.
For example, if the lead has a valid WhatsApp number, you can:
Create an opportunity in a specific funnel and stage
Add the lead to a segment
Start a chatbot
If the lead does not have a valid WhatsApp number, you can create the action "Send a notification to an employee".
Additionally, your flow can be adjusted in various ways, allowing you to customize actions according to the validity of the lead's WhatsApp number. Explore the available options to create the ideal automation for your process.