docs: @Override
  	public Response cancelReserveRN(String corpNum, String requestNum,String userID)
  			throws PopbillException {
  		if (requestNum == null)
  			throw new PopbillException(-99999999, "전송요청번호가 입력되지 않았습니다.");
  
  		return httpget("/FAX/Cancel/"+requestNum, corpNum, userID,
  				Response.class);
  	}