To obtain a portable radio telephone set that easily collects charging by updating call unit information to reduce a speech available time based on unit time information decided by a relative position between a caller and a called party.

A storage section 8 stores information required by processing a control section 7 (e.g. caller telephone number and unit time or the like) and is provided with are residual call unit storage area 9 as a residual call unit information storage means. When a terminal 15 of a reader/writer 14 possessed by a server is mounted on a port 13, a residual call unit number in the residual call unit storage area 9 is rewritten. A system is formed, where the user pays the charge to the server by a residual call unit increased by rewrite by using the reader/writer 14 when the residual call unit number is decreased or zero. Thus, the user uses the portable radio telephone set for a long time without waste by having only to pay the charge.