Not happy about undisclosed extra charges

This morning I stopped in at the Mall @ Carnival McDonald's since I was looking at a day without lunch, I wanted to make sure I ate something. On the screen was an offering "Limited Regular Menu" where medium meals were advertised.

I ordered a 2 Cheeseburger Meal for R47.50. The employee added R2 for a drink despite the sign in question stating clearly "Meal includes medium fries and a medium drink. Available from 6:00am - 10:30am. Tablewear not included. T&C apply."

So if the drink is included, why was I charged extra for the drink? I don't even really care about R2; its the principle of the matter here that bothers me. If I'm going to be charged extra for a drink, signage should NOT say that the drink is included.

If there's some reason for the extra charge, it was not communicated to me clearly and I don't know what its for. Unfortunately I was late for work so I was not in a situation to dispute the issue correctly because I had to leave quickly.