False advertising

I have been buying games at cash crusaders in the checkers center in klerksdorp and they advertise in their Instore radio and on their slips and one of their previous cashiers told me that if you buy seven games you receive one free. Just to find out this is not the case as I have currently a balance of 10 games and every time I ask the cashiers either don't know about it or yesterday I was told that their store doesn't participate in this promotion. How is this?