Misleading advertising

Pick n Pay advertises: \Pepsi assorted 2 x 2 Litre and Lay's Potato Chips Assorted 2 x 125g\" R40. I specially went to the local store to get the special but was not allowed to take a Mountain Dew 2 litre with the special combo deal. Why not? It is a Pepsi. I was told I can only take Pepsi Cola or Pepsi Cola Light but the adverti*****t says Pepsi assorted. I wasted my petrol up and down to the store and returned empty-handed. Please assist urgently."