[otrs] How to switch off SUBJECT field in customer web interface

Hello support, i decided to switch of subject field that customer could not change it when he is doing a follow up and that subject would be the same all the time. I'm looking in system config: Frontend::Customer::Ticket::ViewZoomhttp://otrs.bs2.lt/otrs/index.pl?Action=AdminSysConfig&Subaction=Edit&SysCon... , i turned off a possibility to change priority on follow up, but i cant find a possibility not to show SUBJECT field. Is there another way? I need only text field and possibility to attach files when doing follow up in customer interface. thank you in advance -- Matas Labasauskas