As the name suggests, the big draw of Apple's FaceTime is its ability to make free video calls, but you can also make free audio calls over FaceTime just as easily.
- If you're not already on a FaceTime audio call, start one by launching the FaceTime app, select a contact to call and then tap the Audio button.
- Tap on the screen to bring up the call controls.
- Swipe up from the top of the controls panel.
- Tap the Camera Off button.
Simply tap the same Camera setting to turn it back off again.