Sometimes people ask questions because they want to start a conversation. Maybe they were wondering how many 500-calorie drinks make the Cheers program worth it.
I am sure Carnival will say it is up to your bank and the bank will say it is up to Carnival. We have a similar problem years ago, it took a couple of weeks to resolve it.
I guess all the bartenders and servers on the Breeze, Valor, Glory, and Spirit do not know the rules since they always gave me a full can often unopened.