An object is to create a convergent mediation system (10) and method that provides a good degree of interoperability and ease of administration. According to an aspect of the invention, these objects are achieved by providing a convergent mediation system (10) that comprises a common platform (18) for both online processing (12) and off-line processing (14) of data. The common platform (18) is designed such that it includes a plurality of independent nodes (120, 125) adapted to form processing streams (200) for the online processing (12) of data and processing streams (200) for the off-line processing (14) of data such that each of the processing streams (200) comprises at least two nodes (120, 125) in sequence. Furthermore, the system (10) is provided with at least one online interface node (125) and configured such that the first node in each of the online processing streams (212) is such an online interface node (125). The online interface nodes (125) are adapted to receive data from the at least one of the communications network (30) or the service delivery platform (30) and send a response thereto. The content of the response is selectively formed in one of the online processing streams (212).