It's really not that difficult. Get in touch with someone at Austrian Airlines. All you have to say is..."we were booked on Flilght XXX on (give date). We got notice the flight was cancelled. What alternate flights are you offering?"
It's that simple. No one should give you the runaround. Ask for a supervisor if they do.
If this was on two separate tickets....meaning one for VIE-JFK and the other for JFK-HNL then Austrian is only responsible for the VIE-JFK flight.
If you continue to make your own arrangments without letting Austrian try to come up with a solution.
--you could be out thousands of dollars extra;
--your insurance company does not have to reimburse you because they will say you didn't give the airline a chance to rebook you;
--you may not be covered under EU 261 because you did not give the airline a chance to make it right.
When is/was the flight?