[SR-Users] Send UPDATE to inform changes in SDP

Hi guys, I'm trying to setup a Call Forward No Reply with Kamailio and I've run into this problem (that was expected): When A INVITEs B, B replies with 183 and some SDP. B doesn't answer so Kamailio triggers the timeout and sends the INVITE TO C. C replies with 200 OK and some SDP, but A side drops the call as the media session doesn't match with the expected one. To solve it, I'm trying to send to A an UPDATE before relaying the 200 OK from C. I tried to use UAC module (uac_req_send + $uac_req) but I don't see how I can UPDATE the existing dialog. uac_req_send seems to try to setup a new dialog always. Is there a way to indicate to uac_req_send that I wan't to use the existing dialog? Or maybe there is another mechanism I can use to send the UPDATE inside the dialog? Regards, Alfonso.