I am curious if anyone has ever done this. Is it possible to upgrade after boarding. I am leaving on the Vista this Saturday with a $400 interior room with a window. I have $400 in OBC and $500 in the casino. With all the cancellations there seems to be quite a few balcony and OV rooms available and I am wondering if I can upgrade for a small amount without giving up my OBC and casino credit. I realize this an unusual situation and people probably have not had such an opportunity in the past but thought someone might know of the possibilities. I contacted Carnival by phone but all they could