A measure that would have prevented the telephone company from charging customers for information (411) calls died today when the Maryland House of Delegates sustained Gov. Marvin Mandel's veto it.

A lobbyist for the Chesapeake and Potomac Telephone Co. said later it is unlikely that the charge - which would have to be authorized by the rate-setting state Public Service Commission - would be initiated before late this year, primarily because the company already has a rate increase request pending before the commission.

A second measure, passed like the first by the 1976 General Assembly but signed into law by the govenor, prohibits the utility from imposing a charge on 411 calls before July 1.

An emotion-charged campaign to over ride Mandel's veto of the bill placing a flat ban on the charge was led by Del. Raymond A. Dypski (D-Baltimore). It fell short of the needed three-fifths majority by six votes, 79 to 47.

Dypski predicted that if the giant utility were permitted to charge its customers for dialing information operators, its next step would be to reduce the type size in phone directories, forcing customers to buy information no available free.

Orville Wright, the phone company lobbyist, who watched the vote from the gallery, denied later that the company has any intention of reducing the type size in its directories. On the contrary, Wright said, C & P is "conscientiously looking" at returning to a four-column format, a change that would cost $700,000 more than the present five-column books, he said.

Dypski his voice quivering in an East Baltimore accent, denounced that phone company, saying it "didn't always tell the truth" at hearing before the PSC. He accused the firm of buying the equipment it needed to implement the change plan before getting state approval of the idea. Dypski also passed out a list of delegate telephone numbers in printed small type, telling colleagues they should hang on to it so as to a vert a 20-cent charge for calling information.

The details of any charge plan, if approved, are not known, but one proposal would permit residential customers three free calls to 411 a month, with extra calls being billed at 20 cents each. Persons who dialed 0 instead of 411 would be charged 40 cents. Charges for calling 411 already are in effect in 14 states, including Virginia.

Speaking in support of the veto, Del. Michael II. Weir (D-Baltimore County) said "we're all being ripped off" by phone customers who abuse the free information. A survey by C & P showed that one business called 411 more than 20,000 times in one month.