Federal workers, who are now breaking rules every time they call home to check on the kids or with baby sitters will be able to make such personal calls from the office legally beginning next year.

New telephone rules coming from the General Services Administration also will allow workers on out-of-town business trips to call home daily and charge it to the government.

GSA's guidelines are part of a carrot-and-stick program designed to make office telephone rules more realistic and cut down on abuse of the telephone system by workers making nonbusiness local and long-distance calls. Some agencies have already electronically blocked telephones making it impossible for workers to use various services from dial-a-joke to weather information. The government estimates abuse of the phone system costs nearly $100 million a year, and some agencies are now checking computerized telephone logs and billing employes who have made nonofficial calls.Insurance Open Season

Several members of Congress are sponsoring day and evening seminars to help federal workers and retirees decide which health plan to pick for 1988. Between now and Dec. 11, the workers must pick next year's health plan.

Representatives of the various health plans will be at the meetings, as will government insurance experts, Walton Francis, who wrote the Washington Checkbook magazine's Guide to Health Insurance Plans, and Gordon Brown, secretary of the National Association of Retired Federal Employees.

The first session was held last night by Rep. Steny Hoyer (D-Md.) in Greenbelt. Seminars coming up include:

A 7 p.m. session Thursday at the Old Mill Middle School in Millersville, Md., sponsored by Rep. Tom McMillen (D-Md.).

A 7:30 p.m. meeting Friday at the Social Security Administration's Altmeyer Building in Baltimore. This one is sponsored by Sen. Paul Sarbanes (D-Md.).

A Saturday session, beginning at 9:30 a.m., sponsored by Rep. Frank Wolf (R-Va.) at the Luther Jackson Intermediate School in Falls Church.

A Nov. 16 meeting, at 7:30 p.m. at the Albert Einstein High School in Kensington, sponsored by Rep. Constance Morella (R-Md.).

The D.C. National Guard is sponsoring a health plan fair on Thursday and Friday at the Armory. Some federal agencies have arranged to allow employes to take administrative leave to attend the sessions. For information call 433-5122.Catastrophic Care and COLAs

Many federal retirees are concerned about congressional plans to setup a catastrophic health insurance plan under Medicare because they could be forced to pay higher premiums for coverage they already have. Federal retirees are worried that congressional budget- cutters may limit, delay or eliminate the 4.2 percent cost-of-living adjustment due them in January. Steve Morrissey, president of the National Association of Retired Federal Employees, will talk about the two issues at a 12:30 p.m. meeting today in the McLean Governmental Center. The session is open to all federal-postal retirees.