One of the biggest annoyances of WhatsApp, which we have to share with everyone new to the app. You can not send a message to WhatsApp number without saving in your mobile contacts. The only exception is if you receive a message from someone else inside a WhatsApp chat, you can start talking to them without saving in your phone contacts.
However, there are a few ways to send a message on WhatsApp number without adding theme first, one of which is provided by WhatsApp, though not natively in the app. Here are two of the easiest methods below.
1. WhatsApp’s own wa.me links
WhatsApp provides an official way to send messages an unsaved number, not within the app. As explained in this FAQ, you can start a conversation with any number by going to the web address https://wa.me/. Type the full number at the end of the URL, with the country and region code without + or 00.
Example, you want to chat with this number +1-234-567-8900, go to the URL https://wa.me/12345678900. Type it in your browser and you’ll get the page below with a Message icon. Tapping on to opens a conversation in WhatsApp.
2. Use an app to speed things up
If the above method seems a little confusing, you can use an android app. You just need to enter the phone number, tap a button, and you are taken to a newly-created chat in WhatsApp messenger.
Among these apps, Click to chat is the lightest application without ads and no permissions required to speak of. (Download Here)
Moreover, Direct Message for WhatsApp app same as above, just need to install and dial the desired number and open it in WhatsApp chat.
Another one, Easy Message app is other good alternatives has no ads and with few permissions. (Download Here)