CHATTANOOGA, Tenn – East Tennessee will soon have another new area code, and it’s going to add three more digits to many people’s local calls. Starting Feb. 5, TDS said people will need to dial the 423 or 729 area code to complete all local calls, meaning you’ll need to dial 10 digits. If you try to dial 7 digits on or after that date, the call won’t go through and you’ll hear a message.