Hi, Being new to SIP protocol and PJSIP, I thought to ask if anyone knows the best way to send a REFER message to conference that is out of the initial dialog? And actually what means that the the message is sent out of the dialog, does the initial dialog (created by the INVITE) has to be terminated or how is the message recognized to be out of the dialog? I'm trying to invite more people to a conference I've allready called in, which should be possible with the REFER message according to RFC 4579. But if I send the REFER with pjsua_call_xfer() it seems it is sent within the dialog, and server says: "Cannot Blind Transfer 1 Legged calls" Thanks beforehand for any help! BR, -Lassi Romanainen