[ServiceContract]
public interface IConvert
{
    [OperationContract]
    bool ConvertVideo(string path);
}

public class ConvertService : IConvert
{
    public bool ConvertVideo(string path)
    {
        Console.WriteLine("Converting video... wait 3 sec");
        Thread.Sleep(3000);
        Console.WriteLine("Video converted!");
        Console.WriteLine(path);

        return true;
    }
}

_TubiconClient.ConvertVideo(GetFullFtpPath())

try
    {
        _TubiconClient.ConvertVideoAsync(GetFullFtpPath());
    }
    catch (Exception e) { }

{System.ServiceModel.FaultException`1[System.ServiceModel.ExceptionDetail]:
Error in deserializing body of request message for operation 'ConvertVideo'.
OperationFormatter encountered an invalid Message body.
Expected to find node type 'Element' with name 'ConvertVideo' and namespace 'http://tempuri.org/'.
Found node type 'Element' with name 'ConvertVideoAsync' and namespace 'http://tempuri.org/'
(Fault Detail is equal to Error in deserializing body of request message for operation 'ConvertVideo'.
OperationFormatter encountered an invalid Message body.
Expected to find node type 'Element' with name 'ConvertVideo' and namespace 'http://tempuri.org/'.
Found node type 'Element' with name 'ConvertVideoAsync' and namespace 'http://tempuri.org/').}