WASHINGTON (AP) _ A union representing 50,000 American Telephone & Telegraph Co. workers Wednesday called off a nationwide strike planned for Friday after the company agreed to provide more information on subcontracting of technical and clerical jobs.

But the company still planned to go ahead with Friday's scheduled layoff of 2,800 workers who are members of the Communications Workers of America, said company spokesman Herb Linnen.

In August, AT&T said it planned to eliminate 24,000 ''surplus jobs'' in the information services area. ''The layoffs will continue as well as placement in other jobs in and outside AT&T,'' Linnen said.

He said that by Friday, 10,000 will have left ATT's Information Services unit and half of them will have been laid off. AT&T-IS is the AT&T arm that sells, installs and services computers used in telecommunicati ons.

''Although the company maintained throughout the negotiations that it had the right to subcontract during layoffs, the net result of our talks is that subcontracting of technical jobs has been reduced to the equivalent of 85 jobs nationwide out of a workforce of 22,000 jobs,'' said CWA President Morton Bahr.

The company maintained that this is no change.

The issues in the dispute centered on AT&T's use of other companies to perform work that the union said was traditionally done by unionized workers while at the same time it was dismissing employees.

Linnen said the jobs being performed outside the company include developing sales leads by making contact with potential customers and some installation work, for example when a customer wants to use its own contractor.

Bahr, speaking in Anaheim, Calif., where he is attending an AFL-CIO convention, said subcontracting in the clerical area has been reduced to the equivalent of 900 jobs out of a workforce of 28,000.

''They gave up their right to deal secretively with subcontracting,'' Bahr told reporters.

AT&T said it will give the union monthly reports and quarterly projections of the amount and location and jobs being subcontracting.

In addition to discussions with company officials in Washington, the union had filed an unfair labor practices with the National Labor Relations Board's regional office in Newark, N.J., asking that the layoffs be blocked or workers be recalled.

The union claimed it had a promise from AT&T that workers who transferred to AT&T from the local telephone companies that AT&T used to own ''would not be subject to layoff or reduction in wages or benefits for at least seven years.''

The AT&T breakup occurred on Jan. 1, 1984.