Java Jane

I've been going here for years and love the drinks I've gotten, usually. Occasionally someone unskilled comes through, but overall pleased with what I've gotten. But recently I went to use a stamp card I'd filled up and was told that I couldn't use it for a 20 oz chai. Since when? Almost every single stamp card I have filled up at this place in all of the years I've been getting drinks here has gone toward a 20 oz chai. I know it can't be used for the 32 oz drinks, but I've never been told that for the 20 oz. I wound up not even finishing the drink and don't really want to go back.