The Social Pane is focused to only work well for phone calls that are added from the Social Pane itself. You cannot create an open phone call from the social pane. Any phone call added is immediately completed and works more like a note. This is fine for something like a call center, but doesn't provide any useful information for an open phone call activity. Displaying Customer Not Found is confusing for users. If you set yourself as the Call From, it will show your name as the "customer" in the social pane for that phone call record.