Beyond unprofessional.
I was scheduled for a phone interview.
First time, waited half an hour, never got a call. Had to email them to ask for rescheduling.
Second time, waited half an hour, never got a call. Called THEM and was told "sorry, your interviewer is busy."
No heads up notifications, emails, anything. Who schedules interviews and then does that? Stay away from this unprofessional dump of a place.