changing theme w/o ftp?

hello everyone.
i have just open a blog in wordpress.com and i wanted to use a non-listed theme for it. i read the instructions and tried to upload the files with filezilla, but it seems my router is totally blocking port 21. so… is there a way i can upload files to the host server other than ftp?
i’m sorry if this has been answered before, i haven’t found anything.
thanks.