The problem with the loud echo is caused by the audio settings. You should consult the user's computer where it happens and access the Sound options. Make sure the Microphone is Muted. This way you will avoid echoing, while keeping the microphone turned on. If it's muted, it doesn't mean it's turned off. Alternatively, try to lower the sound of the speaks. This usually causes problems with echo while talking on the VoIP applications.