An apparatus and method used in a home-zone location registering process
in a portable telephone which allows a different charging rate to be
applied to a subscriber based on whether the call connection is made
within the home-zone area. According to the method, the portable radio
telephone stores the home-zone list therein and determines whether the
portable telephone deviates from the home zone area, then the portable
radio telephone automatically performs the location registration process
when the deviation is detected.