MTN won't honour a special deal

On Thursday morning my old phone broke and I had to upgrade my contract for a new device. I noticed on the MTN website that there was a Father's Day special on a Samsung S23+ offering a free watch. I went in store to upgrade and requested the special. The representative had no knowledge of this special. He then proceeded to call the Samsung rep into the store to enquire if he knew about it, he also did not. The rep consulted with another colleague who alleged that it was an online only special (the ad makes not mention of this, when I insisted that they honour the special, the next come back was that the watch was out of stock and I should come back the next day. I again explained to the rep that I urgently needed the device and that I would follow up re the watch with head office the next day. No person at MTN has yet been able to assist me and my latest interaction from them suggests that I took the phone without the watch and am therefore not due the watch. I have the receipt from the store where I made the rep write down that he did not have a watch and that I would query with head office. It has now been a week and I am not getting any further.