how can i fix my servis fridge freezer frost free?

my servis fridge freezer frost free has not been freezing peoperly and the fridge was not cold at all although it sounded like it was working ok its not, i un plugged it and cleaned the filter at the back there was a lot of ice in the freezer we defrost it but now when we put it back on the red light is flashing and it is making the normal fridge nooise the green light is on as well please advise.