Consolidated Edison review: Overcharging

A mysterious charge has appeared on my Con Ed bill called "deposit requirement". It is for $170. I have called and emailed Con Ed about this for several weeks, but have not received an explanation. I have never been connected on a phone call with the company despite waiting 10 minutes or more on the line.

The bill threatens that my electricity will be shut off tomorrow if I don't pay this "deposit requirement." I am otherwise up to date on my payments.