Making international calls is different from traditional local calls. To call friends and family in Oman, you will need to dial your current country code, then the Oman country code, Local area code in Oman, and then the phone number you wish to reach.
For example, if you are making a call from the United States to Oman and you want to call someone in Oman with the phone number 08035555555;
You will dial the United States country code, 011 and then the Oman country code plus 8035555555. Alternatively, you can replace the country exit code (011) with (+).