False advertising

Kfc advertised the Tuesday deal of 15 hot wings for R55 if I remember price correct. I went to kfc in strand in gordons bay road and wanted to go buy the deal as I bought it by kfc in stellenbosch the previous week. On my arrival I ordered the deal and as I looked on the board it says add a large chips to your deal for R19.90 but reqeusted only the wings as I bought other meals as well.

I was told they dont sell the 15 wing special just show I need to take the chips as well and pay R74 and when I asked the cashier but thats not what the add says she told me that the boss said they not allowed to sell it separately.

So why advertise wing special and when I get to a franchise they want to force me to buy stuff that is not advertised with the special. I rather had to buy the normal 10 wings as I already ordered other meals with it.