docs: @Override
  	public CashbillInfo getInfo(String CorpNum, String MgtKey)
  			throws PopbillException {
  		if (MgtKey == null || MgtKey.isEmpty())
  			throw new PopbillException(-99999999, "관리번호가 입력되지 않았습니다.");
  
  		return httpget("/Cashbill/" + MgtKey, CorpNum,
  				null, CashbillInfo.class);
  	}