incorrect pricing?

We decided to eat supper at Simply Asia in Cavendish Square , I queried the price difference between the menu and the advertising sign outside the branch. I was then informed by the manager that they are independently owned and that they do not follow the head office specials. We did order the food which was great. Why do you have branches that do their own thing? I can't use my Simply Asia card either? I paid more than the advertised price. I did take a photo of the sign