Unusual instruction from a cashier

Today at the Maponya Mall branch, I was told by the lady working at the kiosk/cigarette counter that I cannot pay for a (single) consumable item taken from elsewhere in the store at that counter, regardless of whether I also wanted to purchase cigarettes or not. Additionally, I was told that if I wanted to purchase cigarettes along with the consumable (which was a 2l bottle of Coke, by the way), I'd need to go to an ordinary till and ask the cashier to fetch the cigarettes for me. Could you kindly clarify if this is standard practice across all Pick n Pay outlets?