Dim vCodigoFuente As String = ""
    Dim id As String = ""
    Private Sub sms_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        sacarid()
        PictureBox1.Image = ReadCaptcha()
    End Sub
Public Function sacarid()
        Try
            Dim req As HttpWebRequest = CType(WebRequest.Create("http://www.mysms.es"), HttpWebRequest)
            Dim res As HttpWebResponse = CType(req.GetResponse(), HttpWebResponse)
            If res IsNot Nothing Then
                If res.StatusCode = HttpStatusCode.OK Then
                    Dim stream As Stream = res.GetResponseStream()
                    Using reader As New StreamReader(stream)
                        vCodigoFuente = reader.ReadToEnd()
                    End Using
                End If
                res.Close()
            End If
            Dim Lines() As String = vCodigoFuente.Split(vbNewLine)
            Me.id = Lines(0)
            id = Mid(id, 4898, 14)
        Catch
            MsgBox("Error")
        End Try
    End Function
    Private Function ReadCaptcha() As Image
        Try
            Dim UrlCaptcha As String = "http://www.mysms.es/img/image.php?dataid=" & id
            Dim _HttpWebRequest As HttpWebRequest = CType(WebRequest.Create(UrlCaptcha), HttpWebRequest)
            _HttpWebRequest.Credentials = CredentialCache.DefaultCredentials
            Dim _HttpWebResponse As HttpWebResponse = CType(_HttpWebRequest.GetResponse(), HttpWebResponse)
            Dim _Stream As Stream = _HttpWebResponse.GetResponseStream
            Return Image.FromStream(_Stream)
        Catch ex As Exception
            Throw ex
        End Try
    End Function

Dim webClient As System.Net.WebClient = New System.Net.WebClient()
        Dim result As String = webClient.DownloadString("http://www.mysms.es/?nation=0034&number=" & numero.text & "&message=TEXTO&Len=135&gcode=" & captcha.Text & "&dataid=" & id & "&send=Send+SMS")