inconsistent with the HTTP Content-Length 400 error in WCF header after sending a latin special character
using (ToursServiceClient client = new ToursServiceClient())
{
    client.ClientCredentials.UserName.UserName = "test";
    client.ClientCredentials.UserName.Password = "test";

    Tour tour = new Tour();
    tour.Customer = new Customer();
    tour.Customer.FirstName = "ñ";

    InsertTourResult insertTourResult = client.InsertTour(tour);
    Tour insertedTour = client.GetTourByTourID(insertTourResult.TourID);
}

client.GetTourByTourID(insertTourResult.TourID);

tour.Customer.FirstName = "ñ";

tour.Customer.FirstName = "a";

<binding name="BasicHttpBinding_ToursService" closeTimeout="00:01:00"
     openTimeout="00:01:00" receiveTimeout="00:10:00" sendTimeout="00:01:00"
     allowCookies="false" bypassProxyOnLocal="false" hostNameComparisonMode="StrongWildcard"
     maxBufferSize="65536" maxBufferPoolSize="524288" maxReceivedMessageSize="65536"
     messageEncoding="Text" textEncoding="utf-8" transferMode="Buffered"
     useDefaultWebProxy="true">
     <readerQuotas maxDepth="32" maxStringContentLength="8192" maxArrayLength="16384"
      maxBytesPerRead="4096" maxNameTableCharCount="16384" />
     <security mode="TransportWithMessageCredential">
      <transport clientCredentialType="None" proxyCredentialType="None"
       realm="" />
      <message clientCredentialType="UserName" algorithmSuite="Default" />
     </security>
    </binding>