Truecaller's Availability feature makes it possible for you to know if the person you're about to call is busy or not.
For example, if you see a red dot next to that number it means that the person is busy, either on a call, in a meeting or has the phone on silent mode. A green dot indicates that the person is free to talk.
You can also see the last time a user was active in the app through the ‘Last Seen‘ status. For more detailed information regarding the Availability feature, please visit our blog to know more.
You can always turn the feature off or on in the settings section in Truecaller.
Please note: To be able to see someone's availability they must have the app installed and have the feature on.
Availability is activated by default and can be disabled in Truecaller's settings -> privacy center.