As a result of a widespread lack of compliance with telephone sign-up procedures, Harvard will begin discontinuing long-distance telephone service today to nearly one-quarter of the undergraduate population, a University official said yesterday.

Beginning today, about 1500 undergraduates will hear only a fast busy signal the next time they attempt to make long-distance calls from their rooms, according to student telephone project manager Nancy M. Kinchla.

Kinchla said that the University plans to invalidate the personal access codes of all students who have not yet registered for long-distance service on the new phone system during the next two days. "Every student needs to register," she said.

Students who want to continue using the codes they were sent over the summer need to apply through the telephone office, Kinchla said.

A number of students interviewed yesterday were unaware of any cutoff date for the telephone access codes, and several said they had been confused by the subtleties of the University's complex new phone network.

Many students said that they had believed that only one person in the room needed to register for long distance service, as in past years. "I figured someone else would register," said Michael J. Meyer '94, a Wiggles-worth Hall resident, who said he has been using a telephone credit card to make calls.

Elizabeth D. Kilmartin '94, of Mower Hall, said she had wanted to talk with her first-year roommates before registering for specific services with the telephone office.

"They should clarify the description of services," said Kilmartin, explaining that she "had no idea" her code could be deactivated.

"I was kind of lazy about it," Kilmartin said.

Others. however, seemed nonplussed by the iminent loss of long-distance service. Vincent T. Ho '91, a Quincy House resident whose family lives in the area, said he did not bother to register because he does not plan to make any long-distance calls.

"I don't really care [if the code is deactivated]," Ho said.

Other students said that the lapse in phone service would only be the latest in a series of problems which have beseiged the phone system during the past two weeks.

Abraham L. Wickelgren '91, of Quincy House, said he has had his phone disconnected twice this semester for no apparent reason. Kamran Rokhsar '94, of Straus Hall, said that the phone in his room would only take incoming calls for several days last week.

Other students have reported that they have been unable to dial time or weather from the phones in their rooms.

Kinchla described most of the problems as an inevitable part of a battery of the complaints that always arise at the beginning of a new year.

"It's very hectic," Kinchla said.

There were 120 phone repairs during one day of orientation week but that number has now settled down to about 20 a day, she said.

Kinchla also said that there were fewer repairs under the new network than there were last year, when New England Telephone provided phone service.

The University's goal is to complete all repairs within 48 hours after a problem is reported, Kinchla said, adding that the new system had an 80 percent success rate on the worst days this year. On more typical days, she said, the success rate hovers at about 95 percent.

"We sympathize with people who have to wait longer," Kinchla said.