I would visit carnival.com and click that box to have them call you. When booking online there are certain fees that you have to pay that you don't when you talk to a Carnival Personal Vacation Planner.
When I booked my cruise for this coming March, I found a room online and it was a total of around $2550. I called my PVP to see if he could give me a better deal, and we wound up with the exact same room I requested for $2200; $300 cheaper!
I can PM you my PVP name and number if you would like.
*Carnival: Victory 5/13~5/20/2012; Glory 3/13~3/20/11, Freedom 7/26~8/2 09; Destiny 10/30~11/3 '08, 3/2~3/9 '08; Victory 4/15~4/22 '07; Valor 3/5~3/12 '06; Holiday 7/31-8/4 '04; Imagination 6/24~6/29 '02 *Celebrity Equinox 5/14~5/24 '10 *RCI Brilliance OT Seas 6/10~6/22 '08 *Regal Empress 6/16~6/18 '05