After having audio issues with IAX2 Trunks. I decided to use SIP Trunk (BoxA and BoxB). The audio sounds great. After testing things out - I noticed I could not do a double transfer. for example My phone is connected to BoxA. Dialing another phone across the SIp trunk to BoxB. That user can trasfer me to any phone connected to that box(BoxB) but if he tries to transfer me back to BoxA I get a “All circuits are busy” hangup cause 21. BUT if I use “CID NUm Alias” on the phone that’s connected to BoxA and masquerade the num. all the transfers work with that phone???
What am i doing wrong