Oregon residents in the 541 area code should prepare for three new digits: 458.

That’s the new area code that will start appearing in early 2010, when the state Public Utility Commission implements the change to keep from running out of 541 phone numbers.

The new code will take effect as an overlay in the 541 region, which covers most of Oregon. No one with an existing 541 number will have to change it, but any new numbers given out after the change will be assigned the new 458 code.

One thing will change: All Oregon residents will eventually have to dial 10 digits to make a phone call, regardless of where the call goes.

The overlay plan was one of four the PUC considered during a series of informational meetings across southern and Eastern Oregon this summer. PUC Senior Telecommunications Analyst Dave Sloan said there wasn’t ever broad support for any of them. Rather, the overlay simply drew the least opposition.

“There were four options that were looked at, and the other three options just fell out,” Sloan said. “It’s just a matter of pick the best one.”

Other proposed plans would have forced some residents and businesses to change their existing phone numbers – a move that could put a financial pinch on some smaller businesses having to change signs or stationery as a result, Sloan said.

The change leaves Oregon with four area codes in two regions – the 503/971 area in northwest Oregon, and now a 541/458 area covering the rest of the state. The overlay plan will provide enough new phone numbers for 24 years, according to the PUC.

“After weighing the options, we believe this solution is the least disruptive option and will meet the demand for new telephone numbers more than 20 years into the future,” PUC Chairman Lee Beyer said in a released statement. “I’m confident customers will have enough time to make any programming changes before the new area code takes effect.”

Sloan said he expects “permissive dialing” to begin next August, allowing residents to dial either seven or 10 digits on local calls. Within the first few months of 2010, he said, all 541 residents must dial the full numbers.

Following the change, customers won’t see any change in cost. Dialing for 9-1-1 emergency calls will also remain the same.