It is bad to call 911 and hang up.
John is a young child that was just taught about emergency services at school.
John wants to call 911.
John remembers the lesson and only calls 911 later when he witnesses an actual emergency.
John sneaks away a cell phone and practice calling 911 and hang up when the phone begins to ring.
The people in an emergency that John witnessed are saved by emergency workers that John called.
John keeps the emergency lines busy and somebody in a real emergency is unable to get through to 911.