A call center maintains various pools of telephone numbers, where each telephone number pool comprises a plurality of telephone numbers in a geographic area. A call originating to a called number uses a calling telephone number that is selected from one of a plurality of telephone number pools based on the area designated by the called number. An index value is used to select the telephone number from the selected telephone number pool. The selected telephone number is used to as a calling telephone number when originating a call to the called party.