I had a year long rental where Telus internet was included in my rent. When my lease ended, I took my telus modem to Canada Post, which promptly lost it and Telus kept charging me for internet AND the lost modem although I didn't even live there anymore! But the best part of it is that they contacted me 7 months later to let me know that they sent my debt to collections! They didn't even bother to check my current address or to email me with their concerns. I called Telus 10 times, and nobody even tried to solve my issue. Suffice to say, I will never again get internet or anything else with Telus. Their only purpose is to make money off of people.
There's pretty clear instructions for cancelling an account. They even remind you to keep the tracking receipt from the Post Office. Also, access to My Account / My Telus is available for some months after you cancel, so cancellation can be confirmed.
Upon cancelling TELUS Optik TV, Satellite TV or Internet, you need to return your rental equipment by following these steps:
Canada Post does nothing promptly, not even lose things. But you would have had a tracking number with your parcel item, and so CP would know where in the system the loss occurred, and you would have proof of failed return. The fault here is not all on Telus if you don't have proof of return. The only real complaint you have is that Telus was charging you for internet that was included in your rent. That confuses me no end, but then it's early.
As someone who has experienced frustration when Canada Post lost a modem I returned to Bell. I provided them the tracking number for the return, which showed, "Accepted at Local Postal Outlet", and that was the end of them contacting me over it. These modems all have serial numbers and MAC addresses that can easily be shut down when lost or stolen. When you return something, always take a picture of the tracking number with your phone and keep that until they receive it and make a point of calling customer service, waiting the close to 2 hours on hold, and give them that tracking number so they can instantly see you attempted to return it when it pops up in their system that it hasn't been returned.