Disable attended transfer between external calls


There are any form to disable the attended transfer (defaults to *2 code) between external calls ?
Is to avoid that one caller, can call another for free using this feature.
If I disable the t or T parameter the employees can’t transfer, and is not a valid solution. The goal is disable the attended transfer in the external leg of the call.



I’ve been worried about this too.

I tested it, and yep, the outside world can call in and transfer themselves anywhere they want without restriction.

Problem is, the system has options for CALLER and CALLEE, but what we need is INSIDE and OUTSIDE.

Inside extensions are sometimes callers, sometimes callee’s.