In collections. Account closed and canceled a day after it was opened. Need advice.

A year and a half ago, I opened a telus account with the intention of procuring wi-fi for my household. The installation was unsuccessful, the tech took the supplies back and I canceled my plan and closed my account on the phone with an agent the next day. They assure me that everything is closed. I owe nothing and I move on. I procured wifi through another provider and thought I had wiped my hands of this telecom company. 

But, fast forward to two months ago. I come to find out that my spam folder has been collecting emails from collections agencies,  my credit score is tanked, I owe 1600 plus dollars to telus, and multiple collection agencies are threatening to send me to court and garnish my wages. 

Naturally, I freak out. I call telus immediately, and they acknowledge that they made a mistake and will credit my account to essentially pay themselves back for a mistake they made.

"Just ignore it..." they say, as the threat of impeding garnishment hangs over me. "We will credit the account, the file will be pulled from collections in 15 days time, we will call you."

They do not call and during those 15 days I receive 3 phone calls from the collections agency and another email threatening to take me to court and garnish my wages. 

I call them. They tell me that it will now take 7 days for a letter to come. They will call me. Except, they do not call.

I get another letter from another collection agency. They are threatening to take me to court. And then, a telus agent calls me, not to talk about this debacle but to try to sell me on their promotions! The nerve.

 I might have considered it once, but this entire situation that they have put me in, has officially destroyed their credibility for me. 

My current plan is to escalate this as far as it needs to go, if that means being assertive and demanding to speak to someone higher up, I will do it. This is ridiculous.

Does anyone have any advice on how I can escalate this?