Method for providing a caller-based ringback tone sound in case of a non-subscribed called

The present invention relates to a method for providing an arbitrary sound chosen by a subscriber instead of a conventional RBT, more particularly, to a method for providing a caller with an arbitrary sound chosen by the caller instead of an RBT in case that a called is not a subscriber of a called-based RBT replacement service. The present method comprises: a first step, conducted by an exchanger when a call is received from a terminal, of requesting a first trunk connection to other telephone communication network while requesting a second trunk connection to a sound providing means if it is confirmed that the calling terminal has subscribed to RBT replacement service and the called terminal is a subscriber of said other telephone communication network; and a second step, conducted by the sound providing means, of providing the calling terminal with an RBT-replacing sound set for the calling terminal through the exchanger.