Help on trying to write to a file

Hello please i am trying to save the result of an operation where i modified some text in a sample application. The problem is i am having difficulty in trying to loop through all the data.Trying to print out my result to a file, i get only the last line of the file.My code simply refuse to loop and write all the data into a text file but it just writes the last data on the line.Please any help on how i can make this work will be highly appreciated.Once again thanks to all.Below is my code.

Using myreader As StreamReader = New StreamReader("C:\Users\Jamiebones\Desktop\ConsoleApplication1\ConsoleApplication1\PHONE NUMBERS.txt")

          While Not (myreader.EndOfStream)


              Dim line As String = myreader.ReadLine
              Dim strBuilder As New Text.StringBuilder
              If String.IsNullOrEmpty(line) = False AndAlso line.Length > 1 Then
                  strBuilder.Append("234")
                  strBuilder.Append(line.Remove(0, 1))

                  For i = 0 To strBuilder.Length - 1

                      Dim writer As StreamWriter = New StreamWriter("C:\phone numbers.txt")
                      writer.Write(strBuilder.ToString)

                      writer.Close()

                  Next i

              End If

              Console.WriteLine(strBuilder.ToString)

          End While
          Console.ReadLine()

      End Using

Tags: Visual Basic, String, IO