I treat calls like this for what they are - scam calls. Nobody is going to give away a free cruise for answering a survey - considering what a cruise to the Bahamas would cost...
I'll bet at some point (if you get a live person...) you'll get asked for a credit card number, and/or other personal information. Never under ~any~ circumstances give ~any~ personal information, and never give your credit card number if they ask for it. That's a tip off to a rip off!!
If these people are legit - why do they hide their name? Unknown Name is what my Caller ID displayed...
Get Caller ID if you don't have it already. It's worth the money...