sending files to a mainframe

[JSH]

I have a need to send files from a PC to our mainframe. I am able to connect but I can't transfer the files because Core FTP keeps appending my user ID to the front of the filename. How do I send a file up using the exact file name I need to transfer to without having my ID attached to the filename? Also, is it possible to do this from inside other software, to initiate the session and transfer the file automatically by another product?