10-Digit Dialing and New Area Code for the 918 Area Code Beginning March 5, 2011, you will be required to dial the area code to place local calls. Now is a good time to start the habit of leaving your area code when leaving phone messages. Starting April 1, 2011, phone numbers with the new 539 ... Continue Reading » about 10-Digit Dialing and New Area Code for the 918 Area Code – affecting Tulsa Metropolitan area