Unacceptable "service" delivery

For about a year or so, the express tills at the food market at the Pavilion branch is, for the most part, always unaccessible. I've sent numerous emails to the customer services manager at the store and was advised that they will have this rectified. However the problem continues. My husband even brought it to the attention of a manager on the floor at the time (as the queue was wrapping around the aisle) and that manager had the audacity to say that the store wasn't busy, therefore the express tills were closed. This incident occurred at 15:30 during school holidays when the store was extremely busy. I have sent emails to the store as well as customer service, however there has been no response. This incident occurred more than a week ago. Why does this store rarely have the express tills working and why has customer service become so poor?