$dialer.getCallNotConnectedReason
This method returns the reason why a call attempt was unsuccessful.
It should only be used in scripts that have a handler for unsuccessful call attempts using the onCallNotConnected event.
Syntax
The method is called without arguments and returns one of two string values: BUSY or NO_ANSWER.
$dialer.getCallNotConnectedReason(); // => "BUSY" | "NO_ANSWER"