Videotron sent my file to collections. I have never missed a payment/bill in my life!

I received a letter yesterday from a collection’s agency called GCQ that I owe Videotron 129 dollars and haven't made a payment since Nov 2020. This is entirely absurd and unacceptable.
Videotron never sent me any bill or a notice and directly sent my file to collections. Who does that?! At least send me a notice first! 
After talking to two reps and spending an hour of my workday trying to explain the situation to them, they told me that this happened due to a system error on their part when I converted my regular account to HELIX. Apparently, they forgot to update the add-ons and make adjustments and I actually don't owe them anything. 

They got in touch with the collections company and have closed my file. But, if this affects my credit negatively in any way, I will take a legal action against the company. 
Furthermore, receiving a collections letter is insulting and unacceptable where I come from. I have never missed a bill payment in my life and have a good credit history. 

This is harassment! I demand a written apology and compensation for wasting my time and causing stress.