Hello,

How I can bridge two calls in SIP by sending A party an indication to change SDP to B party and start playing the B party annoucement to A so A party will be hearing the ringing of B or annoucement of B.

 A Party                    SIP/GW                      B Party
  1|---------INVITE---------->|                          |
   |<----------100------------|                          |
   |                          |------------IAM---------->|2
   |                          |<=========Audio===========|
   |                          |                          |3
  4|<------183 with SDP-------|                          |
   |<=========Audio===========|                          |
  5|                          |                          |
  6|                          |                          |
  7|                          |                          |
   |                          |------------REL---------->|8
   |                          |<-----------RLC-----------|9
 10|-----------ACK----------->|                          |

Is it possible to change the SDP and make the call communication between A and B directly in preanswer mode?