A Network Function service provider in a 5GC, for managing SRVCC handover for a UE having a voice session anchored in an IMS in a PS domain in the 5GC is provided. The SRVCC handover moves the voice session to a CS domain in a legacy network. The NF service provider receives an SRVCC handover required message from an NF service consumer, comprising information about a target ID of the legacy network and a target transparent RAN container. The NF service provider obtains, based on the information received in the handover required message, a legacy target transparent RAN container comprising information required for the target RAN node in the legacy radio access network to accept the handover, an identifier related to the voice session, an STN-SR and legacy CS domain security information. The NF service provider initiates handover by transmitting the obtained information to the legacy CN over Sv-interface.