It checks if the client has the right messenger.
Automation detects a customer's WhatsApp or Telegram.
Automation rules - Check phone
Automation rules see here.

Phone parameter - List of check numbers, one or more numbers can be transmitted. The result of checking numbers will be positive if only one messenger is found.

Constraints WhatsApp
If you check too many phone numbers without sending messages to them, you will be banned. Only check only phone numbers critical to your business for which you have already received customer opt-in.