in the same context of prepaid system iam also building with PBX Features

here is the my big question always is.

if the user register wtih Openser/ Kamailio

dial other register user. when the any one of them want to connect to conference and bring other user in to conferene

how will that work ?

any reference or clarification will be greate

Kamailio registrat and proxy

asterisk as PSTN and b2bua

Mediaproxy / rtpproxy iam using for NAT

Ram