None of the Subways in my town participate in promotions. Subway corporate advertises $5 dollar footlongs in television ads and in the Subway app which draws people in to restaurants. I think it is deceptive for the restaurants to benefit from the advertising but then say they do not participate after customers have made a point to go there because of the advertisement. I believe it is called bait and switch. I know the stores are independently owned but they operate under and benefit from the Subway name.
Change the policy. If it is a Subway branded store, then sell as advertised. Otherwise, the stores should not be operated as Subway.