FTP question

I keep getting a login incorrect when ftp'ing with Smart FTP Pro
The client assures me that his user/pass is correct but it won't let me in.
Is it maybe I should try a different port? Presently I am using Port 21.
My gut feeling is that the client password is incorrect as that is also
part of the error but I was only checking to see if maybe someone could
tell me if any other setting was incorrect.

Thanks