U.S. POSTAL SERVICE (Washington) - Entering his third month as postmaster general, Anthony M. Frank Tuesday shook up the management of the Postal Service with a series of personnel shifts.

Mr. Frank named two associate postmasters general, Kenneth J. Hunter, to supervise technology and operations, and Edward E. Horgan Jr., to handle international affairs.In addition, consumer advocate Ann Robinson's department was expanded to include supervision of measuring the performance of the mail service, and Mitchell H. Gordon was placed in charge of administrative services. He was promoted from marketing and communications.

Mr. Frank, who had been known as an innovative manager in the banking business before taking over the postal job, also announced that he was shifting the Postal Service's planning operations to report directly to him and separating them from the finance operation.

The Postal Service's board of governors also announced that the agency had rejected a recommendation for lower postage on preprinted return envelopes.

The Postal Service announced that it had suffered a loss of $635 million for the accounting period from Dec. 19 to March 11. The Postal Service had anticipated a lost of $586 million for that period. Higher postage rates intended to put the service back in the black took effect April 3.