A method and system of providing data calls to a subscriber having a data network, such as an integrated services digital network (ISDN), connected to a network switch to enable communication with another party at a fixed rate are disclosed. The methodology discovers a data calls system that enables data calls to be placed over trunk lines for communication with a subscriber having an ISDN with a dedicated ISDN line connected to a network edge switch forming a trunk line of the ISDN in communication with a central office. A plurality of base stations are adapted to make and receive data calls using the ISDN over the trunk line. A billing apparatus charges each subscriber a fixed or flat rate per service period for data calls using the trunk line, for the plurality of stations, regardless of the number of calls using the base stations during the service period.