Charging full prices for marked discount prices

I had a horrific experience in Woolworths Malmesbury today. 4 people before me in the qeue had issues at the tills with item prices. My items was marked buy 2 get one free. The teller rang up all three with 3 different prices. Then they tried to persuade me to get an extra item instead of giving me a refund. It is shocking service. Today broke my camel's back because there are always issues at the paypoints.