I overpaid my bill on Nov. 2022 and up until now April 2023 I still haven't received my money back from Fido. I called numerous times since November 2022 and Fido kept telling me that it was sent out, processing it, just wait for a few weeks etc. It's been so long and there's no progress
Welcome to the community!
Usually, if you pay more on your invoice what happens is that amount sits on your account as a credit and goes toward your next invoice, it's usually not worth the time and effort to ask for a refund because you will receive the refund by cheque and by the time that gets processed your next invoice will be ready.
If you did not get the money back maybe it was actually applied to one of your invoices, you double-check your previous invoices to see if that is what happened.