Washington used to be a city of transition. Every few years folks would pack up their belongings, cash in the equity on their homes, and move on.

Mobility was enhanced by changes in political whims, which led to routine chaos every four years.

Political upheaval is still with us. But now, with high interest rates and stagflation, the urge to move has been stifled, and many homeowners are staying put.

For a select group of Bethesda residents, however, the U.S. Postal Service and the Chesapeake and Potomac Telephone Company have combined forces to provide an adventure in moving without actually leaving home.

The Postal Service is changing the ZIP codes of 107,000 residents of Montgomery County. The phone company is changing hundreds of telephone numbers to make room for a new electronic switching center. Together, the new numbers will mean chaos in some quiet, tree-lined neighborhoods.

According to the U.S. Census, the Washington area grew by less than 5 percent during the last decade. The Postal Service and the telephone company, meanwhile, are restructuring their operations, as if thousands of customers are moving--even if they're not.

As a non-mover, I'll get in the next few months a new ZIP code and a new telephone number. These changes represent progress, in the institutional world of computers and automated mail sorters. They're a pain in the ZIP for me.

Life used to be simpler. I spent the first 18 years of my life with the same telephone number. When ZIP codes came along, I accepted my five digits.

I now live in a wonderful ZIP code that shares, with certain other surburbs, a unique status. Although actually in Maryland, it is--in the eyes of the Postal Service--in the District of Columbia. For years, mail sent to Bethesda, Takoma Park, Oxon Hill, and selected other communities could be addressed to either Maryland or Washington.

As an honorary resident of the District, I regularly receive, unsolicited, mail regarding the New Left, New Right, whales, guns, motherhood, and resorts in Virginia.

Would these people send me stuff if they knew I live outside the Beltway?

I've often wondered why Maryland has so many codes that should be in the District. I suspect that a postmaster's clout is dependent on the number of people to whom he delivers the mail. Just serving addresses inside the District Line would leave the postmaster of the Nation's Capital with the authority of only, say, the postmaster of Dubuque. So postal planners gave him some of Maryland.

Now, new planners are attempting to reverse the tradition, moving hordes of us back into Maryland.

As for the telephone company, they've torn up Beach Drive in Rock Creek Park near my home and are changing all the numbers in my neighborhood.

Spokespeople for the phone company tell me it has something to do with the growth of my exchange. It seems strange that the neighborhood, which has been there for nearly 30 years, is growing so suddenly. They haven't told the school board, which is closing down schools like crazy because the population is decreasing.

The phone company says I will be able to dial directly overseas with my new number. Most of my friends won't notice the advantage.

All of this has presented me with a premature mid-life crisis. It involves much the same upheaval as moving, although there are no closing costs that I know of. I retain an affection for my old ZIP code, which is one number I can remember.

My only hope now is that they don't change the street signs. I may never find my house.