Here's the answer from Carnival's FAQ pages.
Can I receive calls while onboard?
Friends and family may call guests on board via Sea Mobile Shore-to-Ship telephone service. The rate is $9.50 per minute from the United States; additional long distance charges may apply from outside the United States.
1-877-CCLSHIP (1-877-225-7447) – from the U.S
1-732-335-3284 - from outside the U.S
The caller needs to have available the ship name and the guest's name. The charges will be applied to the caller's credit card: MasterCard; Visa; American Express; The Discover Card; Diner's Club.
For customer service please call:
1-866-459-9020 or 954-672-4428
Customer Service Hours:
8:30am to 5:30pm Eastern Standard Time
For additional information Click Here
Laissez Les Bon Temps Rouler!