Charge for supposedly free item.

I just bought Happy Meals for children and got charged for the Apple Juices which were supposed to be free? I argued with lady at till who said it was on the bill for stock purposes but was not in the total, well if you add it was clearly in the total! The R8,20 will not kill me, its the principal on the matter. If they do this to a 100 cutomers a day it becomes quite a nice profit. Store was 17th Quarter, Walmer Park, Port Elizabeth