c# ftp cd disabled

i'm perplexing following formula working:

  twine url = string.format(@"someurl");
  twine user = "someuser";
  twine evidence = "somepassword";

  ftpwebrequest ftpclientrequest = (ftpwebrequest)webrequest.create(new uri(url));
  ftpclientrequest.method = webrequestmethods.ftp.listdirectory;
  ftpclientrequest.usepassive = true; 
  ftpclientrequest.proxy = null;
  ftpclientrequest.credentials = new networkcredential(user, password);
  ftpwebresponse response = ftpclientrequest.getresponse() ftpwebresponse;

this customarily works, nonetheless 1 sole server gives an blunder 500: syntax recognized. change office management noxious problem server, site executive told me .net issues change office management default ftp connections. true? there proceed invalidate that?

edit: i login management line i am repremand directory:

ftp> pwd

257 "/" tide directory