Disgusting service and profiling customer

I go to the randburg gym and on an occasion i use the discovery app to get a smoothie with a breakfast. I went through today and was the first in line, and still deciding on my order...looking between the selected breakfast and meal. The cashier takes another order from a customer , then scans my order for a smoothie. I haven't finished my order and she tells me theres nothing that can be done now based on what she redeemed. I then ask her about the selected meal and she insists i was interested in the breakfast. As a customer i was confused i admit that but the way i was treated was terrible. She actually told the same customer when he got back.. i still need to finish with 'this one'. That was very offensive. She then turned to another lady and helped her , i at that point got very upset and took off with her about it. I ended not getting my order and rather just my smoothie. The persons name was mathiba. I will not be using this outlet anymore!!!