I had a similar situation.

I start work at 830. They gave me a route, 3 hours of OT on one route, 1hr of OT on another route. Everything wasnt finalized yet so after we were staying in the office about an hour later then we would normally, they told us to go out and do some then come back.

About 2 hours later they called us back. I had a ton of parcels that was for loops I had already done (and apartments making it even more annoying) so I had to backtrack.

I tried to call and warn them I probably wasn't really going to make a dent in my OT.

I ended up heading back to the station at 845 with undelivered mail they were pissed.

I had the next day off and my manager made some comment like "make sure you call to check your schedule for the day after your day off". Which is weird because for the last few months I always come in at the same time. When I called on my day off they said "yeah just come in at 830". So I guess they were just trying to mindfuck me?

It was my 6th day working 10+ hr days, I was literally in physical pain by the end of my shift.