I've received several calls from this # over the past 2 weeks. They never leave a message.

Calling the number back results in getting a computer that calls itself Jennifer from Holiday Cruise Line.

I receive 3 or more calls per day from this number asking if I want a free trip. I keep asking them not to call back but they keep calling.  I'm getting really pissed off. Somebody help me.

Try completely ignoring the call so that when they do, they get NO kind of answer from your number. As long as you're answering in some way, they'll keep calling, possibly drumming up ideas to trick you with. They can't play if nobody's answering and get tired of wasting time on empty numbers. You have to be patient and outlast them. That's the easiest and cheapest way to dispose of junk calls. A call blocker or app may be of some help, also.