void SetProxySettings<TChannel>(ClientBase<TChannel> client, 
    bool useProxy, string address, int port, string login, string password) 
    where TChannel : class
{
    if (!useProxy) return;
    var b = client.Endpoint.Binding as BasicHttpBinding;
    if (b == null)
    {
        System.Diagnostics.Debug.WriteLine("Binding of this endpoint is not BasicHttpBinding");
        return;
    }
    b.ProxyAddress = new Uri(string.Format("http://{0}:{1}", address, port));
    b.UseDefaultWebProxy = false; // !!!
    b.Security.Mode = BasicHttpSecurityMode.Transport;
    b.Security.Transport.ClientCredentialType = HttpClientCredentialType.None; // !!!
    b.Security.Transport.ProxyCredentialType = HttpProxyCredentialType.Basic; // !!!
    if (client.ClientCredentials == null) return;
    client.ClientCredentials.UserName.UserName = login;
    client.ClientCredentials.UserName.Password = password;
}

<configuration>
  <system.serviceModel>

    <bindings>
      <basicHttpBinding>
        <binding name="Binding1" proxyAddress = "http://myProxy" useDefaultWebProxy="false">
          <security mode="None" />
        </binding>
      </basicHttpBinding>
    </bindings>

  </system.serviceModel>

</configuration>