Is Lewis Cashback promotion true or **** to customers?

Lewis is currently having a " Get R2000 Cashback on selected items when you buy on credit"

I am an existing customer of lewis since 2014. I app**** for credit which was approved. The manager as well as the sales person of Lewis store branch in Randburg assured me that I will receive my cashback of R700 immediately after the delivery was made. Today almost a week later I am still awaiting my Cashback. I called the randburg store to do a follow up on when I will receive the cashback, the sales person told me that the head office haven't gotten back to him with instead they have been giving him the run around. So what am I to do as a customer if the head office is giving its own employee (the sales person) a run around? I should now do follow ups. I would like to think that Lewis is a reputable store with a good reputation not to up hold it's promises. A promise has been made to me so I believe you will do your due diligence to solve this issue amicably.