I received a call from this number three times - first two times missed the call, third time call came in I answered.
The woman was very polite and sounded American. Call was about offering a free cruise (trying to fill empty cabins) in exchange for recommending the cruise to family and friends - giving positive feedback.
The first question asked was if you were able to go - for me, not able to take time off. I then ended the conversation - no point continuing.
I don't know if this offer is legit, but these offers can be legit. Years back a similar offer for a free cruise in exchange for viewing a hotel - I did accept that offer then, it too was a free cruise. Had a great time on the free cruise and also came back to the cruise line again as a paying customer and told friends and co-workers. By talking about my cruise, some I told did take their first cruise as their vacation afterwards.
For safety measures, remember to use a credit card if paying for taxes, not a card attached to your checking/savings account.
If you accept their offer, call cruise line directly and inquire about free shuttle service from airport to cruise ship. Also you can always call cruise line directly when you get your vouchers.