Starting July 29, all calls made within western Washington will require dialing the 10-digit telephone number.
That's because a new area code — 564 — is being added in August.
New telephone numbers in the 206, 253 and 425 territories will be assigned a 564 area code, initially starting with the 360 area code territory.
Current telephone numbers won't change.
State regulators approved the new area code last year.