Ten-digit dialing for local phone calls begins Sunday.
Both seven- and 10-digit dialing are connected, but beginning Sunday, callers must use the 10-digit procedure.
People who dial only seven digits will hear an automated voice message reminding them to use all 10 digits - otherwise their calls won't go through.
"With people already being used to dialing ten digits on their cell phones, I'm optimistic this change will go smoothly," said Lee Beyer, the Oregon Public Utility Commission chairman.
The main reason for the change is that numbers for the 503 area code are almost used up.
A Portland 971 overlay went into effect in 1999. After Sunday, both 503 and 971 area codes will be available at the North Coast - the last part of the 503 area code to receive the overlay.
Long-distance callers will still have to dial 1, then the 10-digit number. Local callers will have to dial only the 10-digit number.
Communities affected are Astoria, Bay City, Beaver, Cannon Beach, Cloverdale, Garibaldi, Jewell, Knappa, Manzanita, Nehalem, Pacific City, Rockaway, Seaside, Tillamook, Warrenton and Wheeler. They all join the Portland and Salem areas in being served by both area codes.
Qwest has released a document answering most questions customers have about their area codes. Go to (www.qwest.com/announcements/OregonAreaCodeOverlay) to see its answers.
One response says area code overlays allow people to keep their old numbers and area codes. And although there are a few 503 area code numbers available, most new phone customers will use a 971 area code.