Truecaller for Android adds ability to identify unknown number right from your Messaging App. If you are using an Android smartphone, this can be turned on in the Auto Search Truecaller settings, and helps identify unknown numbers from WhatsApp, Line, Viber and Telegram. So the truecaller even gives details for messages from unknown senders.
Identify unknown numbers in different Messaging apps can be turned on in the Settings menu > General > Messaging apps, so user will be notified when unknown number arrives in the messaging App.
This feature is exclusively available only for Android users.
[appbox googleplay com.truecaller&hl=en]
So have enabled features on your smartphone? Comments below .