I'd like to know how this case is called and what to do with it.
We have a PBX Samsung OfficeServ 500 in city A and an older and more simple Samsung PBX system in city B with a 4-channel VoIP bridge between them. All calls from city A are automatically transferred to city B via VoIP. The call operators are in city B and they transfer calls to city B's internal phones. But sometimes we have to transfer them back to city A, so 2 lines are used: one in A-B direction and another in reverse direction to internal phone in City A. So there are several problems: a big audio delay, there's a quality degradation and VoIP 2 lines are used for 1 call instead of none.
How is it called? What should we do to prevent it? As I understand it's a pretty common problem, but I don't know how to Google it.