System for notifying a cellular telephone user that a call involves another telephone located outside of a defined service charge range of user's network

摘要

A cellular telephone network system for notifying a cellular telephone user that a telephone call connected to the user's cellular telephone involves another telephone outside of the defined service charge range of the user's network comprising the combination of assigning to each telephone call to and from the another telephone an identifier for the network of the another telephone, an implementation in the user's cellular telephone for reading the another telephone network identifier and an implementation in the user's cellular telephone, responsive to means for reading the identifier, for displaying a message when the another telephone is in a network outside of the defined service charge range of the user's network. The user is enabled to block such calls from outside the defined charge range whereby additional charges are avoided.