We are doing back to back cruises at the end of this year and CPS were very helpful in sorting out a booking covering both cruises which totals 7 weeks. They quoted the same price for the combined booking as we had paid for the original 5 week booking which we think is a great deal.
My wife and I have had this too. Booking number looked authentic but is not recognised and I haven't booked the cruise mentioned. We are on the one immediately before so quite disappointed cos it purported to be offering us the chance to stay on board for a ridiculously low cost. Just need reassurance our original booking is OK.