"No Security header in message but required by policy" error message when calling a webservice

How do I stop getting this error? There is no certificate for the web service. Am I missing something?

 Dim MyService As TESTWEBSERVICE.test.PersonInfoWebServiceClient = New TESTWEBSERVICE.test.PersonInfoWebServiceClient

        Dim MyResult As test.getPersonResponse = New test.getPersonResponse

        MyService.ClientCredentials.UserName.UserName = "uid"
        MyService.ClientCredentials.UserName.Password = "pwd20"
        Try
            MyResult.response = MyService.getPerson("TED")
        Catch ex As Exception
            MsgBox(ex.Message)
        End Try

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