Forced to purchase for more than R20

Last week I sat down with my fiance' to have a meal after work at the Booysens branch Chicken Licken. We ordered our food and paid with my mastercard, after eating we decide we wanted something to drink so I ordered a Buddy Bottle 500ml as advertised on the menu and flyers all over the shop.

I was refused to use my card and was advised by the cashier that a minimum purchase of R 20 must be made in order to swipe my card.

I know this is in breach of the Mastercard rules as I worked for a financial institute for over 13yrs , when I questioned that this cannot be true , I was told that Head office has instructed them not to accept purchases of less than R 20.

Having no cash I was forced to purchase 2 Buddy bottles which to my surprise came as 440ml little dumpies , to then be told that the suppliers have changed the size ???

Chicken Licken then change your advertising as you are misleading paying clients.

FYI ( mastercard rules ) 5.11.3 Minimum/Maximum Transaction amount Prohibited A merchant must not require, or indicate that it requires , a minimum Transaction amount to accept a valid and properly presented MasterCard or Maestro Card.

I have a good mind to report them to Mastercard aswell as Nedbank as I see that's the POS they currently using.