This is just like the Marriott Hotels scam that went around last month.  They say that your last flight on WestJet has been randomly selected to receive a $999 credit on your next flight.  I'd suspect they would ask for a credit card or some other personal information but I didn't let them get that far.  Knowing that I've never flown WestJet in my life I knew this was a bogus call.  I just yelled at the scumbag on the other end of the phone to take my number off their list.  I then blocked them on my VoIP line.  The problem is they use phone numbers similar to your own, probably somehow hacking the caller ID system, so it shows up as a different number every time.