sending multiple SMS from database on button click

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VB

Am working on School Management System,i want to send multiple SMS of student performance to their individual parents.I have stored parents phone numbers on SQL server.I want to retrieve student performance based on parent phones,however my system is not working if sends first SMS with blank data.Below is code am using.

Imports System
Imports System.Data
Imports System.ComponentModel
Imports System.Text
Imports System.Collections.Generic
Imports GsmComm.GsmCommunication
Imports GsmComm.PduConverter
Imports System.Windows.Forms
Imports System.Drawing
Imports System.IO
Imports System.Data.SqlClient
Imports Microsoft.VisualBasic


Public Class sendS1results
    Dim pdu As SmsSubmitPdu
    Dim phone, grade, mesg As New ArrayList
    Dim a As Integer
    Private Sub sendS1results_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        Call loadCbmTerm()

    End Sub
    Public Sub loadCbmTerm()
        With cbmTerm
            .Items.Add("1")
            .Items.Add("2")
            .Items.Add("3")
        End With
    End Sub

    Private Sub btnSend_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnSend.Click
        Call send()
    End Sub
    Public Sub send()
        Dim con As New SqlConnection(conString)
        Dim com As New SqlCommand
        Dim dr As SqlDataReader
        Dim dat As New DataTable
        con.Open()
        With com
            .Connection = con
            .CommandType = CommandType.Text
            .CommandText = "select * from vS1Phones"
            dr = com.ExecuteReader
        End With
        While dr.Read
            phone.Add(dr.Item(0))
        End While
        con.Close()
        For Each n In phone
            txtPhone.Text = n
            If con.State = ConnectionState.Closed Then
                con.Open()
            Else
                With com
                    .Connection = con
                    .CommandType = CommandType.StoredProcedure
                    .CommandText = "s1Phone"
                    .Parameters.Add("@term", SqlDbType.NChar, 3).Value = cbmTerm.SelectedItem
                    .Parameters.Add("@phone", SqlDbType.NVarChar, 10).Value = txtPhone.Text
                    dr = com.ExecuteReader
                End With
                While dr.Read
                    mesg.Add(dr.Item(0) + dr.Item(1))
                End While
                For Each m In mesg
                    txtMessage.AppendText(m)
                Next
            End If

            'mesg.Clear()
            'txtMessage.Clear()
            Try
                pdu = New SmsSubmitPdu(txtMessage.Text, txtPhone.Text)
                ModemSettings.ms.Open()
                ModemSettings.ms.SendMessage(pdu)
                ModemSettings.ms.Close()
            Catch ex As Exception
                MessageBox.Show("Error when sending SMS")
            End Try

            'txtMessage.Clear()
        Next n
        con.Close()
        'phone.Clear()


    End Sub