Giacomo, thanks for the reply.
When i go to Configuration > Network, i see two interfaces (eth0= wan and eth1=lan) and there's no options for set ftp to public. When i go to Configuration > FTP there are only two tabs ( user and configuration) and none of both have a option for set ftp to public.
I deleted all the firewall rules, firewall objects and port forwarding rules for ftp.
I can't acces to ftp server from WAN yet.
I don't know what else can i do to get the fto server working.