I got a warehousing job on the far side of the city from me. To get there, I was dependent on the busses, but the first bus on the schedule for the day got me there ~5-10min late. This was discussed during my hiring interview and wasn't a problem... In the beginning.
Just over three months working there, the manager pulled me into his office and told me I am required to arrive at work on-time. This needs to be fixed or he will begin writing me up for tardiness. He was the same manager that interviewed me and agreed the 5-10min because of the bus was not a problem. Now he's claiming no memory of this conversation and that It's my problem to fix despite me not having any other options.
This is where I told him; Ok, I guess today was my last day then. I then told him I expect the overtime hours I have not been paid, to be on my final paycheque.
This warehouse worked 4 x 10hr shifts per week, instead of the typical 5 x 8hr. This had not been discussed during my interview, I actually didn't find out about it until my first day, when I went to leave after 8hrs. I live in BC Canada. BCs Employment Standards Act requires overtime be paid for hours in excess of 40 per week, as well as more than 8hrs per day. This means the ninth and tenth hour of each shift, is overtime, per BC law.
BCs ESA does provide a method of averaging hours across a week; allowing 4x10hr shifts without overtime. That requires a written and signed agreement between both parties though. I hadn't even been told the schedule, let alone signed such an agreement. I hadn't really pushed back about this though, because I was ok having an extra day off each week, it was still only 40hrs; this was basically just a matter of missing paperwork.
When I told the manager I expected to be paid that overtime, he brushed it off and told me to collect my stuff and get out. Even had a supervisor escort me around to ensure I didn't take or damage anything.
I left and immediately headed to the Employment Standards Office in my city. They took the details and opened an investigation. It wasn't a super fast process, but 3ish months later I received a cheque in the mail, as well as a call back from the ESA Office: the company apparently fired their entire HR department and backpaid myself as well as all current staff a years worth of unpaid overtime, to avoid direct fines and a possible lawsuit. All over some missing paperwork for an arrangement most of the employees were happy with anyway. They even ended up paying for my Employment Insurance claim, because EI agreed I was essentially forced to quit - ie fired without cause.