Yes, IMO calls are free of cost. You have to download the IMO app which is available on IOS and Android phones.
You can start a video call or an audio call easily. Select the contact from your address book. Tap or click the contact to open a texting window and select the video button to start a video call or select the audio button to start an audio call. It’s also available on the desktop with the same process.
Even you can make a group so that you can do the video chat with every contact simultaneously.