Montgomery County is the land of a thousand civic groups, a place where residents so love communing with local government that one wry social observer says the official motto should be "Meet You at the Public Hearing."

So what's a good way to shake up a hyper-organized citizenry? Change thousands of county government phone numbers, as Montgomery officials announced yesterday they would do this month when they switch to a deluxe new phone system.

Starting June 28, callers trying to reach most Montgomery government offices will need to dial a new 240 area code and three-digit exchange to question a property tax bill, lobby a County Council member, get a pet license or request details about many of Montgomery's myriad services. The change will affect 7,800 of the county's 12,000 government numbers.

The impending switch is the latest example of just how inconvenient progress can be two years after 10-digit dialing came to Maryland. Cell phones, pagers and fax machines continue to gobble up phone numbers, forcing big organizations like the county government to reserve huge blocks of new exchanges and take on separate area codes.

Now the almost 1,000 civic associations registered with Montgomery's planning board must overhaul their carefully cultivated Rolodexes, computerized phone lists and dog-eared phone books, soon to be rendered obsolete by advancing technology.

"That's going to be the pits," said Alice K. Helm, a devout Montgomery activist who recently helped set up a one-stop hot line for county senior services that will have to be retooled. "I don't know about progress. It's all semantics. It doesn't mean it helps anyone. You feel very powerless in this kind of situation."

Montgomery is only the latest local jurisdiction to scramble its numbers in response to the increasingly crowded telecommunications market. Fairfax County government changed numbers seven years ago when it moved to a new headquarters building, and Northern Virginia is scheduled to get a new area code and 10-digit dialing in April.

Montgomery last changed its phone system 12 years ago at a time when there were only 2,000 government extensions. For at least that long, all Montgomery government numbers -- except those of satellite offices -- have started with the digits 301-217.

But in less than two weeks, more than half will begin 240-777 or 240-773, meaning that county government extensions will fall under two area codes. That's because the new 240 area code serves much of the same territory as the 301 area code, so neighbors now can have different area codes. Many of the county government's four-digit extensions will remain the same, and Board of Education and school numbers will not be affected. The cost of calls will not change, even if the different area codes are used.

"What it does is really disrupt life and the interaction of citizens with government at a time when they feel disenfranchised," said Jorge Ribas, president of the Montgomery County Civic Federation.

County officials say that they realize the change will be disruptive, but that the time is right to reserve new phone numbers as the balance of available 217 exchanges shrinks. By reserving 777 and 773 exchanges, the county has the capacity to handle 20,000 lines as it brings on a $5.1 million central phone system.

"In six months, they may no longer have been available," said Dennis M. Rooney, communications chief for Montgomery's telecommunications division.

Bruce Romer, the county's chief administrative officer, said Montgomery will spend $250,000 this summer on a publicity campaign to outline the changes, including mailing a summary of the numbers to all 230,000 county households.

Also, county officials will make new internal phone books available to civic associations in a form that can be easily reproduced for newsletters. For the next three months, callers dialing old numbers will reach recordings with the new ones.

"The whole reason we're doing this is to take advantage of technology," Romer said. "Certainly this will cause a lot of consternation, but citizens are getting used to these rapid technological changes."