At my work there's staff and award. Staff people don't get any overtime but are expected to work long hours. Award people get paid overtime if it's organised by the company.
Make sure everything is in writing. If it was said verbally, assume the conversation never happened. Always follow up with "as per our discussion can you please confirm I will do x in return I will receive overtime/time in leui". Then just tell process it and if there's any objections refer back to the email.
There aren't many workplaces who won't try their luck. If they don't follow through don't do any work outside normal hours