Steers wacky Wednesday special price variation

Steers advertises 2 burgers for the price of one( R69.90 )as there wacky Wednesday special. You have choice of chicken, beef or vegetarian. Their adverti*****t is non specific on price until the bill arrives. The chicken and veg wacky Wednesday burgers are more expensive than the Beef. The advert does not state the difference of prices. I had to go with the price put forth by the manager and his cashier. When requested to show proof of the advertised difference, the manager could not.