Canada Post has made it very easy to contact them through various channels:
You can document a request online by tapping on any of the help offices (e.g., bundle conveyance issues, postage rates, apparatuses, and administrations, and so on);
Different channels incorporate online media (Twitter @canadaposthelps and Facebook)
A hotline (1-866-607-6301 for individual and 1-877-262-5762 for business issues)