I work at BP Landsborough QLD as a console operator with a…

I work at BP Landsborough QLD as a console operator with a small amount of kitchen work involved and have been their for 1 year. All staff work as Casuals on a set roster and my shift was from 4am (must be there 15-20 min early) to count tills and set up shop and bowsers.(unpaid) until 9am or 5.30a.m until 10.00 am. We were being paid $20.00 per hour before tax and $25.78 on a Sunday. As there has been a question made about wages we were happy to find out we were given a pay rise this week.$22.25 base $23.67 for early starts and $33.50 Sunday. As we are all casual we are kept on 4 -5 hr shifts and lucky if we get 20hrs in a week. We just found out today as we received a pay rise we are all losing an hour on several of our shifts, so in fact now earning even less with less hours. We were informed as we are being paid more it would work out the same for us.
I get out of bed at 3am so I can be at work by 3.40am and now I am told to only work 4hrs. I was informed that we could write a letter to request part time to receive the benefits of a part time worker but the pay would be greatly reduced . I am not the only one questioning this as one worker has been their for 4 years at the same rate and and feels loyalty obviously means nothing anymore Can you tell me if this is the correct pay and if we would benefit from part-time employment and time off for a holiday would be something to look forward too