Roter Hahn Restaurant Clarens beer measurement incorrect

On 03/01/2019 we had brunch and drank a couple beers , we had 4 La Trappe Blonde on tap , on the menu the price listed for 300ml was R 65-00 , the glas it was seved in was marked 0.25 L ( 250ml ) , the account presented to me showed R 65-00 for 330 ml. I complained and request the waiter even before the account was delivered that I am not prepared to be charged for 300/330 ml but only to receive 250ml. He spoke to management but they did not fix my account and I was presented with a bill for R 56-00 for 330 ml of the mentioned beer . I then spoke to management and it was an issue to resolve the situation , the lady even told me at a stage that the price for the 300 and 250 ml is the same on their system so I the bill is correct. I insisted that I would not accept the situation and eventually they removed one beer form the account . According to my calculation they make an extra R 15-00 profit per glass with this by presenting a smaller glass than advertised.