Misleading 3 for 2 promotion

It's not fair when clients are sold one story and the reality is totally something else. I purchased Gillette Fusion Pro glide blades on the Clicks online platform and I just wanted blades and it so happen that I selected the qty of 3 packs of the 4 blades and proceeded to check out.theywere running a 3 for 2 promotion on this item. The purpose of the 3 for 2 is that you pay for 2 and the cheapest 1 is free.. These blades cost R299. 99 per 4 pack. The check out price was R598 for 12 blades... When I recieved my package I see there was only 2 packs in the box. I was sent a mail saying that due to no stock at the time I only got 2 packs and I can chose to get back R199. 00 in refund to my card OR R250 in the clicks club card... This is incorrect as the promotion is 3 for 2, I never got 3 packs and also if I just now go and buy another pack as their Customer services tell me then I have an pay an addiitional amount from my side of R50 due to Clicks being unable to fulfill their promotion which is not my fault and should not be the consumer problem.. There are enough stock on the shelves in store and surely 1 pack can be swhere else.. This is very disappointing service and misleading.