Chesapeake & Potomac Telephone Co. has told the District's public service commission that it will reduce basic telephone rates for residential and business customers by 52 cents a month if the agency approves a new charge for information calls.

In testimony prepared for a public hearing on the issue Monday, C&P rate planning administrator Maureen K. Grandmaison says a relatively small number of D.C. customers place directory assistance calls.

By making the customers who use the service pay for it, C&P could save $1.9 million in the initial year of such charges, she states. This savings would permit the reduction in basic rates.

Although other subsidiaries of American Telephone & Telegraph Co. have been seeking to charge customers for information calls, C&P of Washington is the first in the nation to propose an accompanying reduction in rates.

Two AT&T firms - New York Telephone and Illinois Bell - credit bills 30 cents a month in exchange for charing customers that make more than a certain number of information calls each month.

In the case of the District, C&P is seeking a rate structure that would permit three calls to directory assistance each month without charge.

Additional calls would cost 20 cents apiece. There would be no charge for information calls from pay phones, or by hospital patients, hotel guests and the handicapped.

C&P of Virginia now charges 10 cents per information call above a monthly allotment of six. In Maryland, the General Assembly has blocked C&P's information charge proposal, partly because of lobbying by telephone workers who see a loss of future jobs.

AT&T companies now are charging for information calls in 24 areas of the country. The D.C. commission had denied C&P earlier request to charge for information calls in 1976.

In Grandmaison's testimony for the new rate request, she cites the following data from telephone company studies:

Each year, about 24 million information calls are made by D.C. customers at an annual cost to C&P of $5.5 million.

Of all D.C. customers, 39 per cent place no information calls in a month, while 70 per cent call three times or less a month. Fifty per cent of all information calls are made by less than 9 per cent of C&P customers. About 900 resident customers call C&P for information more than 50 times a month.

About 7 per cent of information calls are for numbers not yet listed in telephone directories and 3 per cent are for unlisted numbers.

On average, Grandmaison says "Customers make less than one call per month for a number not available in the local telephone directory."

Although not all C&P customers are supplied routinely with telephone directories for all area phones - one book each for Maryland, Virginia and the District - C&P spokesman F. W. Chamberlin said yesterday the company provides any of the directories on request. He said only about 5 to 6 per cent of these customers ask for the extra books.