Coercion to buy under false pretense

I bought some clothing at Legit and Edcon was running a promotion whereby if you purchase clothing to the value of R350 or more you would receive a R100 gift voucher. Firstly at the store they did not know how this promotion works yet it was advertised at the pay point in-store. Eventually this lady tried to assist me but it turns out the system didn't allow me them to.They took down my details to forward to head office. Head office was supposedly going to contact me and provide me with a voucher number. 3 weeks later I'm yet to receive a phone call. It's become clear to me that the ladies at the store as well as Edcon are just hoping that I will forget about this and carry on with life, but how many other customers have been ****med in this way because that's what this is....a ****.