I had a similar issue with my Samsung phone..
I took it to the store 2 times and then said I want something done.. made a lot of noise.. scared away customers (by telling them about my warranty issues with them)..
One of the younger fellas said to me.. they have a 3 time lemon agreement or something.. 3rd repair is the last before a full refund or replacement..
According to CGA you have to give them the chance to make it right.. 2 times.. maybe 3 times? and then they are in breach of the act if they fail to replace or refund after a fair and reasonable chance to make it right..
I've found the warehouse group to be quite good when it comes to CGA.. however.. it comes down to the store and their manager's knowledge of the act..
If they're a chain store company (spark.. vodafone for example..) then maybe try another store?
The grief the store is giving you seems like a lack of knowledge/experience of their end..