Read your payslip, and know who to ask when it looks wrong
Checking your pay is not distrust. It is basic maintenance, and it is easiest done monthly.
A payslip is a record, and records only work if somebody reads them. Get into the habit of opening yours every pay cycle and checking that the basics match your own notes: the hours you actually worked, the dates of the period, the rate applied, any deductions listed, your name and details spelled correctly, and superannuation showing where it should. Keep your own record independently, because the whole exercise depends on having something to compare against. A note on your phone with the date and the start and finish times of every shift takes ten seconds and settles almost every dispute before it becomes one.
We are not going to tell you what you should be paid, what you are entitled to or what any rule requires, because pay and conditions are legal questions and they turn on details of your specific job. What we will say is that noticing early matters. Discrepancies that get raised in the same month are usually corrections. The same discrepancy raised a year later becomes an argument about memory. Keep your payslips as files rather than as glances, keep them somewhere you will still have access to after you leave, and keep them in one place so that the record is a record rather than a scatter.
If something looks wrong, start by asking your employer, politely and in writing, with the specific dates and numbers attached. Most problems are administrative and get fixed at that step. If you are not satisfied with the answer, or if you would rather understand the rules before you raise it, the national workplace authority is the correct source, and your institution's student support service can usually point you there and help you word the question. Do not take your position from a housemate. Take it from the body whose job it is, and take it before you resign in a temper.