Hi,
You can load the file using the file collector or use FTP file download and export the file to the same location with the new name.
If you are using file collector:

file collector basically moves your file from current directory to storage directory.
if you are happy with this renaming you are all good or you have to use export file of ftp activity to load it back in the current directory.
the second option would be mount this FTP location as a network drive and use js to rewrite the file with new names.
Regards,
Amit