Freddie, thanks. I knew about 011 for accessing USA when in foreign country; Silversea also lists 99 in their documents. In fact, the full statement in the docs is:
To dial the ship directly without using a credit card, you will first need to dial your local Dialing code (i.e. 011. 99) plus the telephone number or fax number shown below:
Caps and punctuation are exactly as shown in documents. I think I will use Ngaire's office as contact number,