The present invention relates to a Gateway of Supplementary Services, PABX and Centrex, which makes available supplementary services to subscribers, PABX and Centrex subscribers, in a centralized and uniform way, to any type of subscriber (analog, digital, x DSL, V5.x, wireless, movable cell telephone or public telephone) belonging to the Commuted Public Telephone System (CPTS), connected to the telephone central of any technology (analog or digital) of any size (large-size, medium-size or small-size). One of the objectives of the present invention is achieved by means of a system of centralizing services to subscribers of various origins in telephone networks, the system being characterized by comprising: a Gateway (100) provided with a central control unit (1); a subscriber service unit (3); a database and data storing unit (5); the central control unit (1) being associated to a telephone network, the telephone network comprising centrals of the public network, the subscriber service unit (3) comprising functions of answering subscribers, stored in the database and data storing unit (5), the Gateway (100) comprising, in the database and data storing unit (5), a virtual calling number of the subscriber, the virtual number of the subscriber corresponding to the subscriber recognition number in the telephone network, the subscriber recognition number being deleted from the local central of the public network associated to the subscriber and transferred to the Gateway (100).