1. Start by dialing the exit code for Australia, which is 011.
2. Next, dial the country code for the United States, which is 1.
3. After that, dial the area code for Texas, which is usually a three-digit number (for example, 972 for Dallas).
4. Finally, dial the seven-digit mobile number of the person you are calling.
So, to call a mobile number in Dallas, Texas from Australia, you would dial: 011 1 972 XXX XXXX.