Exxon said it will honor Sears' Discover card in Georgia and San Diego . . . AT&T said it is asking the Federal Communications Commission to allow price cuts on phone calls to 32 foreign countries by an average of 10.1%, a reduction of $150 million a year . . . Borg-Warner Corp. reported that it will begin purchasing all properly tendered shares of Chilton Corp. at $33 per share in cash . . . American Cyanamid reported that three unprofitable chemical products will no longer be produced at its Linden, N.J., plant, which will mean 400 layoffs.