Dissatisfied customer

I was buying some items and went to go pay at the tellers and this lady from teller 8 or teller 10 I'm not sure which one is it, instead of putting the sign that she is closed she lets me wait on the que until I get to be the last person only to my surprise she then puts out the sign that she's closed. I then confront her but she blatantly ignored me as if I was not even there. I was horrified by her attitude to say the least, if that is how they treat their customers I'm afraid that they are going to lose customers.