That or press the green bar flashing on the top. Just like switching to another app when you are in a call using a 3G or 3GS. Press the Home button, and you'll see the green bar flashing across the top, but the call is still active and you can continue your audio only conversation.. Press that green bar or the Phone app and your right back to the Phone screen. Or with the case of FaceTime back to your video call.