code: @Override
  	public String FAXSend(String CorpNum, Statement statement, String sendNum, String receiveNum, String UserID)
  			throws PopbillException {
  		if (sendNum == null || sendNum.isEmpty())
  			throw new PopbillException(-99999999, "발신번호가 입력되지 않았습니다.");
  		if (receiveNum == null || receiveNum.isEmpty())
  			throw new PopbillException(-99999999, "수신팩스번호가 입력되지 않았습니다.");
  		
  		statement.setSendNum(sendNum);
  		statement.setReceiveNum(receiveNum);
  		
  		String PostData = toJsonString(statement);
  		
  		ReceiptResponse response = httppost("/Statement",
  				CorpNum, PostData, UserID, "FAX", ReceiptResponse.class);
  		
  		return response.receiptNum;
  	}
docs: /* (non-Javadoc)
  @see com.popbill.api.StatementService#FAXSend(java.lang.String, com.popbill.api.statement.Statement, java.lang.String)