Code to model a phone

Hi, just wondering if someone can look at my codes and see what's wrong.

Code:

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Public Class Form1

    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load

    End Sub

    'Digit keys
    Private Sub key1_Click(ByVal sender As Object, ByVal e As EventArgs) Handles key1.Click
        callDisplay.Text &= 1 'Button for "1"
    End Sub

    Private Sub key2_Click(ByVal sender As Object, ByVal e As EventArgs) Handles key2.Click
        callDisplay.Text &= 2 'Button for "2"
    End Sub

    Private Sub key3_Click(ByVal sender As Object, ByVal e As EventArgs) Handles key3.Click
        callDisplay.Text &= 3 'Button for "3"
    End Sub

    Private Sub key4_Click(ByVal sender As Object, ByVal e As EventArgs) Handles key4.Click
        callDisplay.Text &= 4 'Button for "4"
    End Sub

    Private Sub key5_Click(ByVal sender As Object, ByVal e As EventArgs) Handles key5.Click
        callDisplay.Text &= 5 'Button for "5"
    End Sub

    Private Sub key6_Click(ByVal sender As Object, ByVal e As EventArgs) Handles key6.Click
        callDisplay.Text &= 6 'Button for "6"
    End Sub

    Private Sub key7_Click(ByVal sender As Object, ByVal e As EventArgs) Handles key7.Click
        callDisplay.Text &= 7 'Button for "7"
    End Sub

    Private Sub key8_Click(ByVal sender As Object, ByVal e As EventArgs) Handles key8.Click
        callDisplay.Text &= 8 'Button for "8"
    End Sub

    Private Sub key9_Click(ByVal sender As Object, ByVal e As EventArgs) Handles key9.Click
        callDisplay.Text &= 9 'Button for "9"
    End Sub

    Private Sub key0_Click(ByVal sender As Object, ByVal e As EventArgs) Handles key0.Click
        callDisplay.Text &= 0 'Button for "0"
    End Sub

    Private Sub keyNumsign_Click(ByVal sender As Object, ByVal e As EventArgs) Handles keyNumsign.Click
        callDisplay.Text &= "#" 'Button for "#"
    End Sub

    Private Sub keyAsterisk_Click(ByVal sender As Object, ByVal e As EventArgs) Handles keyAsterisk.Click
        callDisplay.Text &= "*" 'Button for "#"
    End Sub

    Private Sub keyDEL_Click(sender As Object, e As EventArgs) Handles keyDEL.Click
        callDisplay.Text = callDisplay.Text.Remove(callDisplay.Text.Length - 1, 1) 'Delete the rightmost character currently shown on the display area
    End Sub

    Private Sub keyClear_Click(sender As Object, e As EventArgs) Handles keyClear.Click
        callDisplay.Clear() 'Clears the display area
    End Sub

    Function displayLength() 'Phone number input user

        'displayInput = callDisplay.Text.Replace("*", "").Replace("#", "") 'Remove "*" and "#" from the digit count

        If callDisplay.Text.Length = 10 Then
            Return 1 'Proceed with Rule#1-Local Call
        ElseIf callDisplay.Text.Length = 11 Then
            Return 2 'Proceed with Rule#2-Long Distance Call
        ElseIf callDisplay.Text.Length = 12 Then
            Return 3 'Proceed with Rule#3-Long Distance Call
        ElseIf callDisplay.Text.Length = 3 Then
            Return 4
        Else
            Return 5
        End If
    End Function

    'Rules for dialing
    Private Sub keySend_Click(ByVal sender As Object, e As EventArgs) Handles keySend.Click 'Case selector

        Dim displayMsg As String
        Dim caseSelector As Integer

        caseSelector = displayLength(callDisplay.Text)

        Select Case caseSelector

            Case Is = 1 'When input length = 10
                'If the number is 10 digits, it should not begin with “0”, “1”, “911”, or “555”.
                If callDisplay.Text.Substring(0, 1) = "0" Or callDisplay.Text.Substring(0, 1) = "1" Then
                    displayMsg = "Can't Complete Call to: " & callDisplay.Text & " (invalid first digit)"
                ElseIf callDisplay.Text.Substring(0, 3) = "911" Or callDisplay.Text.Substring(1, 3) = "911" Then
                    displayMsg = "Can't Complete Call to: " & callDisplay.Text & " (invalid prefix 911)"
                ElseIf callDisplay.Text.Substring(0, 3) = "555" Or callDisplay.Text.Substring(1, 3) = "555" Then
                    displayMsg = "Can't Complete Call to: " & callDisplay.Text & " (invalid prefix 555)"
                Else
                    displayMsg = callDisplay.Text & " Call Sent (Local)"
                End If
                callDisplay.Text = displayMsg


            Case Is = 2 'When input length = 11
                'If the number begins with a “1” it should be 11 digits – long distance.
                If callDisplay.Text.Substring(0, 1) = "1" Then
                    displayMsg = callDisplay.Text & " Call Sent (long distance)"
                ElseIf callDisplay.Text.IndexOf("555") = 1 Then
                    displayMsg = "Can't Complete Call to: " & callDisplay.Text & " (Invalid prefix 555)" 'if final 10 digits start with 911
                ElseIf callDisplay.Text.IndexOf("911") = 1 Then
                    displayMsg = "Can't Complete Call to: " & callDisplay.Text & " (Invalid prefix 911)" 'if final 10 digits start with 911
                Else
                    displayMsg = "Can't Complete Call to: " & callDisplay.Text & " (Invalid first digit)" 'if number starts with other digits

                End If

                callDisplay.Text = displayMsg

            Case Is = 3 'When input length = 12
                'If the number begins with “01” it should be 12 digits – long distance.
                If callDisplay.Text.Substring(0, 2) = "01" Then
                    displayMsg = callDisplay.Text & " Call Sent (long distance)"
                ElseIf callDisplay.Text.IndexOf("555") = 2 Then
                    displayMsg = "Can't Complete Call to: " & callDisplay.Text & " (Invalid prefix 555)" 'if number starts with 1555
                ElseIf callDisplay.Text.IndexOf("911") = 2 Then
                    displayMsg = "Can't Complete Call to: " & callDisplay.Text & " (Invalid prefix 911)" 'if number starts with 1911
                Else
                    displayMsg = "Can't Complete Call to: " & callDisplay.Text & "(Invalid first digit)"
                End If
                callDisplay.Text = displayMsg

            Case Is = 4
                If callDisplay.Text = "911" Then
                    displayMsg = callDisplay.Text & " Call Sent (Emergency)"
                Else
                    displayMsg = "Can't Complete Call to: " & callDisplay.Text & " (Invalid length)"
                End If
                callDisplay.Text = displayMsg

            Case Is = 5 'all other input length
                displayMsg = "Can't Complete Call to: " & callDisplay.Text & " (Invalid length)"
                callDisplay.Text = displayMsg

        End Select

    End Sub
End Class

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I don't know why but I keep getting the message "No default member found for type 'Integer'"...
Also, what should I do to make the program to recognize input such as "222222222#" 9 digit + "#" is not a valid input?

Thanks!