Lil miss I don't wanna do this right now

I had a chilling experience. From entering the place, the cashier didn't greet us and wasn't very open to our questions regarding to the flavor my cousin wanted. We ended up choosing the wrong flavor and immediately asked if we could change it. Annoyed as she was, she told us it's too late and that's not possible. I don't think we would've minded if she wasn't so rude and reluctant to help us, which made us insist we want to change the order. The manager stepped in and told us the order hadn't gone through yet and she can still help us change the order. I hate being a difficult customer and I absolutely understand that life sometimes get the better of us, and there are days you can't show up with a smile but through it all practise kindness especially with customer service businesses.