A very impressive feature whats app have introduced that if you want to send text to a number that is not saved in your contact list then you can use whatsapp api. Using this API you can send pre defined text to any number. Here is snapshot attached. This image is to show how api is called. Just provide phone number with country code and without 0 in start and then provide your text. Click send button and you will see following interface.
Just press send button and message will be sent to unknown or unsaved contact. Thats all. 🙂