Is there anyway to get a category room upgrade on an already purchased Carnival Cruise?

We’ve purchased the cruise already for March; is there any way to get a free upgrade from Carnival?

How can I convince Carnival Cruise Line to upgrade me to a balcony from an oceanview for free?

I have been on 6 previous carnival cruises, and have never had a balcony and really really want one! Please Help! Thanks!
It is 3 of us, 2 adults, and 1 teenager. Newlyweds idea wont work!!