If it wasn't for my mortgage I'd walk out on my job today. When we were shut down I was promised first shot at the place opening two blocks from my house. Today they tell me they've filled all the hours so I have to continue at a store miles away that I hate. Ugh.
Do you have any sort of proof that this was offered? An email or something along those lines?
If so, then considering they've also done you over on the whole part time / casual thing, I'd be ringing fair work Australia and lodging a complaint.
One mistake... Yeah, I could believe it but when you start to see a whole bunch of f**k ups going against one person then it sounds to me like they are working towards making your life miserable for a reason.
At the very least, I'd be telling them that you want your leave and part time status re-instated. They should be able to fix that. It's not their right to just pay you out if thats not the way you want it to go.
