Thomas J. McCall, 53, Lansford, has been appointed acting postmaster in Lansford, it was announced by J. M. Donaldson, postmaster general in Washington D. C. He will begin his new duties at midnight tonight, succeeding to the post made vacant by the recent death of William J. Cannon, who had served in that capacity for 13 years. The salary pays $5,790 a year. He will be obliged to withdraw from all political activities as a result of the appointment.