public IHttpActionResult register(SendOTPModel sms)
        {
            if (!ModelState.IsValid)
            {
                return(BadRequest(ModelState));
            }

            var error   = String.Empty;
            var message = String.Format("ANN.COM.VN - Ma OTP cua ban la: {0}. Ma se het han trong vong 5 phut. Cam on!", sms.otp);

            try
            {
                var result = _service.bulkSendSms(sms.phone, message, 0, out error);

                if (!result)
                {
                    return(BadRequest(error));
                }
                else
                {
                    return(Ok());
                }
            }
            catch (Exception ex)
            {
                return(BadRequest(ex.Message));
            }
        }