From what I understand, refare means you have the same booking number which your deposit is attached to, but adjust the room and price in this booking number. Rebook means the booking number is void and deposit is refund. All the other purchases like spa, cabana or CO will also be refund if only if they are refundable, because they attached to the booking number. A new booking is made on the new condition.
If you found a better deal or same deal with a better cabin, you can ask for change. Only problem is You may loss the promotion or OBC attached to the current version of booking.
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i just did a refare for the new crew appreciation promotion. My current cabin is obstructive VH and it is no longer available for 3 people. So I was quoted the next normal VH from the website. Turn out, with a better cabin, my price remind almost the same, plus the added crew appreciation. It is no brainer for me to upgrade to new VH and get the crew appreciation. I will however lose my OBC from the obstructive VH. And I am ok with it.
for your senario, if your inside doesn’t have 3 people anymore when it is 400 cheaper, then how much is an ocean view? Chances are, ocean view is also cheaper. You may not get $400 back, but you can ask for a better room. If I were you, check the next category, if it is same price, switch and get the new promotion.
and don’t forget to regard to non refundable price a few days before final payment. It will save you a copy hundreds there.