Something isn't right. They are mirroring the orbitz IVR tree an to some degree the script but this number doesn't show up on Orbitz' website.
This could very well be that they have recorded Orbitz IVR tree and are trying to sound similar to achieve the same effect. When I asked her why this number isn't listed on Orbitz website she said that the numbers are sometimes random when they call people...? Either way, NEVER call back the 800 number that called you, always go to the official number on your receipt.