How to stop iPhone calls going directly to voicemail. Go to Settings via the cogs icon on your iPhone home screen. In the second batch of options underneath Notification and Control Centres there’s a purple icon with that crescent moon and the words Do Not Disturb.Click on that. Move the slider on Manual so that it is off – so there's no green on that Manual slider.ou are not alone. For some unknown reason many iPhones suddenly switch to a curious setting that sends most iPhone calls straight to voicemail in iOS 7. Luckily there’s an easy fix. First check whether you have Do Not Disturb set on your iPhone.