Can you clarify what you're asking? Are you having a problem? What Unity version? Which switch integration?
"loop back" can mean a few different things - the most common item is if you have message notification turned on to a phone that is set to forward to Unity again - Unity calls that device and it "loops back" to itself and Unity ends up talking to itself. By default if we see the calling number is one of our own ports, the call terminates and all is well. If, however, the call goes to a remote device (i.e. a cell phone) which forwards back to us and does not provide the calling number information then it can be a problem. There's an option for Unity to play a special tone out when answering the call that we can detect to determine that we've called ourselves in this scenario. It can cause a bit of a delay on transfers, though, as we have to play/detect this tone before completing the call which can burn 2 or 3 seconds. Not a huge deal but some folks find it annoying.
If you can clarify what problem you're having and what your configuration is, we may be able to help more.
