Very unprofessional.
After making contact with a partner in the Technology practice I was referred to an HR Manager who rescheduled a first telephone interview four times in one day, 30-60mins AFTER the interviews were scheduled to start. The manager didn't even blink an eye in recognition that she was wasting my time and behaving extremely unprofessionally.
Deloittes values include 'Talk straight' including being respectful of other people's (time, etc...) however I have not seen this demonstrated by their HR team.
Deloitte are now no longer a target company of mine. Moving on.