Bad service with rude staff

I have had this experience now so many times where the cashiers think they are doing you a favour by assisting you. I shopped at Checkers Blue Crane last Friday - cashier dumped some of my stuff on counter (even though I did not limit the number of bags she was to use). First, she wanted to put chocolate with warm food I purchased - when I friendly pointed out one can't do that, she just mumbled she was going to put it on top of the hot food in bag and then, instead of giving me another bag, proceeded to dump it on the counter, together with one or two other things. She obviously did not like it that a customer dared to say something to her (even though I was NOT rude). I still thanked her, but got no response whatsoever. I then had to do another purchase as I forgot about pancakes I ordered and still had to pay for - I thanked her again with same lack of response. I then (still not rude) asked her why they are so unfriendly, that I thanked her twice now without any response from her and that friendliness costs nothing. She literally rolled her eyes at me and turned her back at me without saying a word. I asked another lady where the manager is, but she was not very helpful either, hence me reverting to writing a review. Very frustrating, rude and bad service that is really not necessary. There are a lot of other shops I can buy from, and their service can really improve (quite a lot). I am also not the only one complaining about this - Checkers is becoming known for their bad service.