Bad service and pricing

I went to McDonald's on Sandown Road. And I ordered 2 triple bbq burger meals which come with coldrink. I asked to swop the coldrink with a mocha from the McCafe. The lady helping me said she could not get it working, so had to ring it up separately. So I said ok. Then just after paying, I realised the total price of R128.80 was too much and I questioned it. She said she did not ring it up as a meal and done the items separately. The meals are R40 each and mochas R20. So that would have been R120. But I am paying R8.80 more and not getting 2 coldrinks. So I asked her to change it and I will then just take the coldrinks. She said no, I cannot change it now, because I already paid. And then gave me food before they even started making my coffee. So I had to ask them to make new food so it is not cold by the time I get him. But it was just put under warm light. I will not be returning again with bad service like this