Well if you have taken a Carnival cruise before they usually send you carnival magazines in the mail and your guest number is on it. Or you can call Carnival and they have the number. We booked our trip through our travel agent and our travel agent called Carnival to book us a room and they had our number just by giving Carnival our name. I hope this helps. Debbie
There are several areas of information on carnival.com that will not allow access to unless a past guest # is entered. It's only natural you would wonder what secrets are behind the locked door. Frustrating. Never hurts to ask.