WORKING HOLIDAY VISA EXPIRED

We are french and we have a australian working holiday visa, it's very important to know this for the next. We travelled with Jetstar on 17th september, flight JQ 205 from Sydney to Auckland. In order to make our check-in we went at Jet star office H10-18. Your hostess, Nancy, told us ; you can't take this flight because your visas are expired since the 14th september 2011, we were very surprised to hear it. We tried to explain her the fact this type of visa permit to stay in Australia during one year, and we arrived the 26th december 2010. She didn't want to hear us so we asked her to speak to skilled people (her manager and immigration department). And she told us it was impossible.
Then, she told us we can't go back in Australia and we didn't able to take the flight to New Zealand if we didn't have a return for another country (excepted Australia). She brought us to Jestar service desk and her colleague gave reason to her.
So we had to buy a flight from New Zealand to Noumea (french polynesia), we paid $AUD 634,40 with Air New Zealand. When we returned for the second check-in, with another Jetstar hostess all it was good with our visa and she was very surprised about her inquiry. Then we passed the customs and we checked with the immigration officer the visa's validity and he confirmed our visa is in order.
We are very surprised about the fact a hostess can take this kind of decision without check with the immigration department. That's why we ask a full refund of the flight Auckland-Noumea.