Where you right to Carnival complaining or telling them how good your cruise was. They will send you a letter back telling you thank you or if you are lucky they will say call us back at this #, 45 days before your next cruise.
Then you will call them 45 days before your next cruise and they will ask you what you want. I can't remember what the choices used to be, but that is basically what it is.
It is a shame they aren't doing it anymore, a lot of people probably won't write anymore. But I guess in these times they have to do, what they have to do. Anyways they are selling cruises pretty cheep now, so that is good.