A local consumer group yesterday called on the Chesapeake and Potomac Telephone Co. to halt an advertising campaign that says District residents are paying too much for telephone service, charging that the promotion is "deceptive and misleading."

Ann Brown, chairman of the Consumer Affairs Committee of the Americans for Democratic Action (ADA), and Fred Goldberg, committee counsel, said they had written a letter to C&P president Thomas M. Gibbons complaining about the ads, which tell how much money customers would have saved on telephone bills if C&P could offer the controversial Optional Measured Service (OMS).

The savings cited in the ads were based on a comparison with flat rate charges--$8.83 a month for a dial phone with unlimited local calling. But Brown and Goldberg complained that C&P was wrong to omit from its comparison the economy rate--$2.20 a month for a dial phone plus 4.9 cents for each local call.

"To omit recognition of this service . . . has a tendency to mislead the public," Goldberg said.

C&P representative Web Chamberlin said the comparison was fair and valid because 86 percent of the D. C. telephone customers now use flat rate service. He said the company will respond to the group's letter, but that the ads will continue.

With OMS rates, customers' charges are determined by the number of local calls they make, the length of time they talk on each call, the distance involved and the time of day when the call is made.

The OMS program, which now is an option for telephone customers in 41 states, is opposed by many consumer advocates. The telephone company describes the program as a way for consumers to pay only for the telephone time they actually use.

C&P efforts to implement the OMS rate locally were rejected last year by the D. C. Public Service Commission. The commission said then that the company, before resubmitting its request for OMS rates, would have to show that consumers are interested in having it. Company officials said the ad campaign, begun in mid-February with radio and newspaper ads, was an attempt to build that interest.