McDonald's SA - Milkshake order mess-up

<p>Ordered the biggest size shake at the drive through in Banana Flavour for the promo running. After payment I received a Choc shake. After telling the lady at the window to replace and give me the choc shake for free as well she looked to the manager and the response was no. I told her about the **** service and asked to speak to the manager and the manager then passed a message to the lady at the window stating that she won't. This is ********* and the customer needs to wait for order due to incompetence. </p>