IMS call control nodes and methods are disclosed for providing online charging in an IMS network. An IMS call control node receives a call message from a CSCF through a first interface for a call session, and determines whether to execute Application Server (AS) logic or gateway logic responsive to the call message. If the processing system determines that the call message should be processed with the AS logic, then the processing system executes the AS logic to perform a service and to contact the OCS for online charging for the service. If the processing system determines that the call message should be processed with the gateway logic, then the processing system executes the gateway logic to perform call session control and to contact the OCS for online charging for the call session.