at command - reading from cell phone inbox

hi all,
im trying to read from a gsm modem's inbox using AT commands. when i run this code, the only response i get is "OK" but i should be getting the message from the inbox. my code is bellow:

Code:

---

    Private Sub viewInBox_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Dim comSerial As New System.IO.Ports.SerialPort


        Try

            With comSerial
                .PortName = "COM5"
                .BaudRate = "9600"
                .StopBits = IO.Ports.StopBits.One
                .DataBits = 8
                .Parity = IO.Ports.Parity.None
                .ReadBufferSize = 10000
                .ReadTimeout = 1000
                .WriteBufferSize = 10000
                .WriteTimeout = 10000
                .RtsEnable = True

                .Open()
                .DiscardOutBuffer()
                'for reading sms
                .DtrEnable = True


                .Write("AT" + vbCr)    'execute command on buffer
                .Write("AT+CMGF=1" + vbCr)
                .Write("AT+CMGL=ALL" + vbCr)

                Dim Incoming As String = .ReadExisting()

                MsgBox(Incoming)
               
                .Close()

            End With

        Catch ex As Exception
            MsgBox(ex.Message)
        End Try

    End Sub

---

my only guess would be that its only writting out the last part of the string. if so, how would i concat all the string parts into one? if thats not the problem, what is?