Combinational networks may provide simultaneous connectivity over networks of different network types between user equipment. A communication session, comprising a circuit switched call and one or more packet switched sessions, may be deployed simultaneously over different network types, in relation to the same user equipment. The circuit switched call and the packet switched session can be correlated, in which case the communication session is regarded as a combinational session. By introducing a number of logical databases that contain actual data on network addresses and communication sessions, a correlation check is deployed applied by a correlation node. The check consists of a number of queries towards said databases or to other network entities, yielding whether the communication session is to be regarded as combinational. The result of the check may e.g. be deployed in an on-line combinational charging system.