shell calls don't work for FTP

I am making calls to WinScp.com from the command line via my program. This works fine for sftp using certificates, but I cannot use the 'call' command to invoke commands remotely for ftp servers. I just need a way to ascertain if and when certain remote files exist on the ftp server.

For instance, when I type:

winscp> call ls

I get repetitive messages telling me that it is switching to ASCII mode, then to binary mode and finally "500 Unknown Command".

Any ideas:

Thanks

With FTP you can execute only FTP commands with call. I'll update documentation to cover that.