A method of processing a call signal in a mobile terminal, the method comprising: setting user status information for indicating a plurality of different statuses for a user in an instant messaging service; receiving the call signal when the instant messaging service is implemented using the mobile terminal; confirming caller information corresponding to the call signal; processing the call signal independently from the user status information if the caller information is related to a specific caller, wherein the processing comprises outputting a feedback informing the user that the call is received; searching a call signal response mode mapped to the set user status information when the caller information is not related to the specific caller; outputting the feedback in response to the received call signal when the searched call signal response mode represents a normal response mode when the user status indicates an 'on-line' status; and processing the received call signal as a missed call when the searched call signal response mode represents a no response mode, a call unable response mode or an off-line response mode such that the feedback is not output in response to the received call signal, wherein the no response mode is selected when the user status indicates an 'empty' status, the call unable response mode is selected when the user status indicates a 'busy' status, and the off-line response mode is selected when the user status indicates an 'off-line' status, wherein the call signal is processed such that the mobile terminal is unable to respond in response to the selection of the no response mode, wherein the call signal is processed such that the mobile terminal is unable to connect to a caller in response to the selection of the call unable response mode, wherein the call signal is processed as if the mobile terminal is powered off in response to the selection of the off-line response mode, and wherein the user status information is registered to at least an external instant messaging service server and a signal managing server even when the instant messaging service is not running on the mobile terminal. setting user status information for indicating a plurality of different statuses for a user in an instant messaging service; receiving the call signal when the instant messaging service is implemented using the mobile terminal; confirming caller information corresponding to the call signal; processing the call signal independently from the user status information if the caller information is related to a specific caller, wherein the processing comprises outputting a feedback informing the user that the call is received; searching a call signal response mode mapped to the set user status information when the caller information is not related to the specific caller; outputting the feedback in response to the received call signal when the searched call signal response mode represents a normal response mode when the user status indicates an 'on-line' status; and processing the received call signal as a missed call when the searched call signal response mode represents a no response mode, a call unable response mode or an off-line response mode such that the feedback is not output in response to the received call signal, wherein the no response mode is selected when the user status indicates an 'empty' status, the call unable response mode is selected when the user status indicates a 'busy' status, and the off-line response mode is selected when the user status indicates an 'off-line' status, wherein the call signal is processed such that the mobile terminal is unable to respond in response to the selection of the no response mode, wherein the call signal is processed such that the mobile terminal is unable to connect to a caller in response to the selection of the call unable response mode, wherein the call signal is processed as if the mobile terminal is powered off in response to the selection of the off-line response mode, and wherein the user status information is registered to at least an external instant messaging service server and a signal managing server even when the instant messaging service is not running on the mobile terminal.