A device of a first network function (NF) is provided. The device includes memory including instructions, a transceiver, and at least one processor, wherein the instructions, when executed by the at least one processor individually or collectively, cause the device to obtain load information for representing a load of each NF in an NF group including a second NF and a third NF, determine whether each NF in the NF group is in a first state representing an overload of a NF by using the load information, based on determining that the second NF is in the first state and the third NF is in a second state different from the first state, change a ratio between the second NF and the third NF for distributing a plurality of calls from a first ratio to a second ratio different from the first ratio.