If all you're doing is extending your benefits to the end of the month, it sounds like the manager is just being an ass. He's clearly in the wrong and I don't think you should hesitate to call his boss. Just explain there's clearly been a mistake but it has to be resolved. I doubt you'll even need to threaten them lawsuits. If you want, you can probably just make it clear that you since you've "quit/retired/whatever", you have lots of time on your hands so you'll be sure to "keep in touch daily" to make sure the matter gets resolved. They'll fix it just to make to you leave them alone.
:-D
This was the plan I've settled on and thought I should come back to update. The fact that I contacted their office and was told that I would be covered should be enough. Also, people who resign and people who retire pay the same amount toward their benefits. It makes no sense that one group would be advantaged over another. It would make more sense if he said no one was covered to the end of the month.
So, I'm not even going to bring up age. Also, I am hoping that this guy's boss will see that I'm willing to pay back the overpaid salary if they fix the benefits problem and it might be difficult to get that money back if they piss me off.
It's weird with the overpayment. They overpaid me but then need to pay me for a retroactive raise. They want me to pay back the overpayment and then they will cut me a cheque for the retroactive raise once I've paid them back. Why not just ask for a lower overpayment and not send me a cheque?
I've asked around and unlike in some of the employers of others in the thread, there is no real definition of retired. As for needing to be over a certain age in Ontario, I'm not sure. I don't think so. But I really don't know for sure.
Thanks for the input, everyone.