On Instantgo, users who are your friends and family can usually contact you for free (as long as a user had your contact number in their phone, they can by default reach you for free on Instantgo as they could simply use your regular phone to call you). You can easily manage who can contact for free by going to your "Settings", clicking on the "Contacts: tab and accessing the "Free" option. There you can easily manage your list of free users.
You can also easily check if a chat conversation, texts or messages are getting paid or is free by simply looking at information on a chat screen. Find below an illustration that explains how you can check on your screen while texting who and if someone is paying for the discussion.