Settings for making telephone calls when out of my home country

I am based in Austria and currently in the US. When I try to make calls, I automatically get 'call failed,' which seems to be a setting on my phone as it doesn't even try to connect with a carrier. I tried changing the settings for my contacts in the US; for example, when I call my sister from Austria I need to dial '001' so I changed this to what I would use in the US, but no luck - any suggestions?!

Thanks!