Ridiculous service

I was in Shell field street, Durban. I saw a promotion for two participating nestle bars for R16. 90. I took two from the displayed items and went to the counter. I was told the promo isnt coming up. I proceed to show them that its displayed and the dates are still applicable. I queried as to which bars are participating. I was told that they dont know. I do not understand how they could display a promo with a price point and not know which items are participating. I find this ridiculous. Then I am told if I have a problem to complain to shellSa, by a gentleman in a white shell shirt. What kind of service is this? I went again today and the said gentleman walked close to the counter and gazed at me. Great customer service right there.