OZ has nothing to do with it. A very common fraud designed to trap people who do not confirm the website they are on.
It is a fraud. You more than likely used a search engine to look up the carrier and that number popped up without confirming that it was the Austrian website you were on.. If you run the phone number you dialed, you will see that it comes up for a wide variety of travel services and airlines.
Always best to assure that you are on the website for the carrier in question. If you run Austrian and then see that its website is
www.austrian.com, you will also find the correct phone number on its website.
Particularly important because you provided your credit card number to a fraudulent operation and should consider asking your card issuer for a new card.
A fraud for sure, but very easily avoided.