It is simple and very obvious.... If you visit a cruise lines website, call them, go on a cruise -- any of those. They will have your number in their database. They then call you to see if you are still interested in cruising.

These people are called Travel agents, Vacation Planners, Personal Cruise Consultants, etc.

Basically, they provide customer service along with insides on any specials and promotions running.

This is a cruise line that says you used them before and has "deals" specials for your next cruise. I have never been on a cruise before so I have no clue how they got my number. Also they left you a voice mail telling you to call them back.