code: public void processRefer(long timeout, int statusCode, String reasonPhrase, int duration,
        EventHeader overrideEvent) {
      setErrorMessage("");
  
      PhoneB b = new PhoneB(timeout + 500, statusCode, reasonPhrase, duration, overrideEvent);
      b.start();
    }
docs: Same as the other processRefer() except allows for a couple of overrides for testing error
  handling by the far end outbound REFER side: (a) takes a duration for adding ExpiresHeader to
  the REFER response (the response shouldn't have an expires header), and (b) this method takes
  an EventHeader for overriding what would normally/correctly be sent back in the response
  (normally same as what was received in the request).