Rain Cheque - Pick n Pay Herm****

I have a rain cheque for Omo Liquid Ultra 900ml that has been out of stock for the past month. I checked in store at least twice a week to see if the item is in stock. I spoke to one of the managers named Nicholas at least three times regarding my rain checks for this item. He assured me that they would extend the date of the rain check if they don't have it in time or source it from another branch or make a plan to honor the rain check. This morning I checked again, no stock, called to speak to the branch Manager Wayne who has now told me that they are unable to honour the rain cheque because it was an instore promotion. As far as I understand is that if a price is shown on a shelf and the product is out of stock a raincheque is issued. I love shopping at pick n pay herm**** but this has now completely changed my thinking about pick n pay herm****. hope to get an answer on this. Kind regards Roxane