We Can use This Application as an reference for validating the Indian Mobile numbers which starts with 6,7,8,9 only.

Make sure you enter mobile number of 10 digits only. (Don't use +91 or 0 before mobile number).

Mobile number will be validated and then WhatsApp Web will be opened for you and only you have to hit send click to send message.

Make Sure that you are logged in to WhatsApp Web  or WhatsApp Application on your systems.