Thanks Floger for giving more details on what happened to you, that is a terrible experience. I am not saying this is the case but some factors to consider. I suspect the long power outage had some impact on the CE's network especially if they were on Videotron as I know they lost network stability after 24 hours of the outage. Even after 6 days of the outage, Videotron was still struggling to get all of their networks back up (from my point of view).
Try to call them (CE) back and ask for an explanation of why it drained your account like that. They should be able to email you a detailed transaction so you can verify it against what you have from the App's history.
I encourage you to try again and see if it happens again, I'm sure you will find that things are much more stable now. Or at least rule out that it was a one of incident.