Senior managers smoking at entrance of Steve's Spar Blackheath

How does a customer go about getting a store to prevent its senior staff members from smoking cigarettes at the entrance to the shop? At least a couple of the senior managers at Steve's Spar Blackheath on Beyers Naude Ave are smokers - not a habit that I personally like, but frankly none of my business - until they smoke right outside the front door of the shop, do not react to requests to refrain from smoking there, or respond to emails sent to them complaining about the practice. Of course it is not merely a case of satisfying a grumpy customer, but complying with legislation...