Upon calling number back, female voice says number is not in service - this is followed by a fax tone.

I think this one is a scam.  The recording when you pick up says you have won a free cruise and press 9 to redeem the prize.  I looked the number up on a US site and they are in Florida.  my husband got sucked into the trap before and we ended up paying money for a free trip and had to spend days doing time share tours.  If you didn't do the tours you had to pay for everything on the trip.  (Only free thing really was the hotel which was crap).

Call received today, but I don't answer this type of call.  Caller ID was unknown