Telus balance sent to collections?

Has anyone else had a Telus balance sent to collections without ever being contacted about it?

I recently noticed that my TransUnion credit score dropped by about 100 points, from roughly 860 to 760. I've never  missed a payment on anything. When I checked my report, I found a collection for only $115 from a collection agency, with TELUS listed as the original creditor.

The strange part is that I've been a telus customer continuously for at least 10-12 years and I've lived at the same address for the last six years, and my current Telus account is in good standing with a $0 balance with autowithdrawal enabled.

As far as I'm aware, Telus never contacted me about an outstanding balance. I didn't receive a bill, email, phone call, or any indication that I owed $115. I also don't recall ever being contacted by the collection agency. If someone had simply told me I owed $115 I would have paid it.

I've started a dispute with TransUnion because I don't recognize the debt, but I'm trying to understand how this could happen. If I genuinely owed $115, why wouldn't it have appeared on my existing account, or why wouldn't TELUS have contacted me before sending it to collections? They have my current account and contact information and I've remained an active customer the entire time. 

So now I'm so bummed because my near perfect credit score has been wrecked from this charge for a hundred bucks.

Has anyone else had something similar happen with TELUS? If so, were you able to find out where the balance came from and get the collection removed from your credit report?