Method to establish and control a conference call between several subscriber terminals (T, T1, T2, T3, T A, T B) of a telecommunication and/or IP network (PSTN), in particular subscriber terminals connected to different network nodes, characterized in i) that a request for the setup of a conference call is transmitted either directly from a subscriber terminal (T, T1, T2, T3, T A, T B) or from an agent terminal (1, 2, 3) of a call center to a switching computer or data network server in the network, in which at least one routing information item pertaining to the participant of the conference call is stored, ii) in that in the switching computer or data network server, based on the routing information, a connecting structure of the conference call optimized from the capacity perspective is calculated by means of a calculating unit, iii) in that, as a function of the calculation result of the calculating unit, the connection to the subscriber terminals (T, T1, T2, T3, T A, T B) of the conference call is automatically established and controlled by the telephone switch (VST1, VST2, VST3) best suited for the switching computer or data network server from the capacity and cost perspective, iv) in that, one or more alternative connecting structures are calculated by the switching computer or data network server from the capacity and cost perspective, if currently a high line utilization or other technical problems occur(s) with the optimized connecting structure, and v) in that, to setup the conference call, in addition to the connection setup request, data pertaining to the alternative connecting structures are transmitted to the selected telephone switch (VST1, VST2, VST3), and the selected telephone switch (VST1, VST2, VST3) or telephone switches (VST1, VST2, VST3), in the case of a capacity deficit or technical problems, transmit(s) the connection setup request and the associated data of an alternative connecting structure in each case to an additional telephone switch (VST1, VST2, VST3) selected in accordance with the alternative connecting structure, as a result of which an automated switching is possible. i) that a request for the setup of a conference call is transmitted either directly from a subscriber terminal (T, T1, T2, T3, T A, T B) or from an agent terminal (1, 2, 3) of a call center to a switching computer or data network server in the network, in which at least one routing information item pertaining to the participant of the conference call is stored, ii) in that in the switching computer or data network server, based on the routing information, a connecting structure of the conference call optimized from the capacity perspective is calculated by means of a calculating unit, iii) in that, as a function of the calculation result of the calculating unit, the connection to the subscriber terminals (T, T1, T2, T3, T A, T B) of the conference call is automatically established and controlled by the telephone switch (VST1, VST2, VST3) best suited for the switching computer or data network server from the capacity and cost perspective, iv) in that, one or more alternative connecting structures are calculated by the switching computer or data network server from the capacity and cost perspective, if currently a high line utilization or other technical problems occur(s) with the optimized connecting structure, and v) in that, to setup the conference call, in addition to the connection setup request, data pertaining to the alternative connecting structures are transmitted to the selected telephone switch (VST1, VST2, VST3), and the selected telephone switch (VST1, VST2, VST3) or telephone switches (VST1, VST2, VST3), in the case of a capacity deficit or technical problems, transmit(s) the connection setup request and the associated data of an alternative connecting structure in each case to an additional telephone switch (VST1, VST2, VST3) selected in accordance with the alternative connecting structure, as a result of which an automated switching is possible.