[Freeswitch-users] Terminating calls prior to answer using api

Hi, I'm having an issue gracefully terminating calls prior to them being answered. When I issue the uuid_kill command prior to the call being answered my sip client gives an error "unable to connect" with an error tone. Is it possible to cancel the client dial without causing an error? Maybe using a sip notify message or something? I can't seem to find a list of valid sip notify messages anywhere. Thanks