Extra money for no consideration

On Tuesday I went to KFC, and I purchased 4 nugget boxes at 29.90 each. I get to the deive through because I have a sick toddler I don't have the liberty of getting out of the car. The lady at the window says it's 50 in the drive through. I said where does it say that?? She says it's a cheap meal if i want it cheap i must go inside i say i cannot coz my child is sick she says well then its 50 rand! Honestly now! No sign! No consideration! And for 50 not even a extra anything in the box. No more ridiculous could anyone get!