From WhatsApp:
To format an Israeli phone number for compatibility with WhatsApp, you should use the following format:
+972 [area code] [phone number]
Note:
* +972 is the international calling code for Israel
* [area code] is the 2-digit area code (e.g. 03 for Tel Aviv, 04 for Haifa, etc.)
* [phone number] is the 7-digit phone number
Example: +972 3 1234567
This format will ensure that WhatsApp can recognize the number as an Israeli phone number and allow you to send messages or make calls.