Finally cleaning out my saved voice mails, and I found that I had more than a few calls from these scammers. The calls from "Alert" started in  August 2013 from 7085294734. I only hear the end of the robocall in my VM, which says "Press 5 to be transferred to one of our friendly representatives".

Caller ID                      Phone number     Date
Alert                            7085294734       Aug 26, 2013
Alert                            7085294734       Sep 18, 2013
ENERGY BILL             8475928794       Nov 11, 2013
ENERGY BILL             8475928794       Nov 13, 2013
ENERGY BILL             8475928794       Nov 18, 2013
CAUTION                    7085294728       Nov 22, 2013
ENERGY BILL             8475928794       Nov 22, 2013
ENERGY BILL             8475928794       Nov 26, 2013
SERVICE CUSTOME  7085710690       Dec 30, 2013
SERVICE CUSTOME  7085710690       Jan 3, 2014
SERVICE CUSTOME  7085710690       Jan 10, 2014
ENERGY SERVICE     7085294767       Apr 16, 2014
SERVE POWER          7085710612       Jun 10, 2014
CUSTOMER CARE     7085294712       Aug 5, 2014
CUSTOMER CARE     7085294712       Aug 29, 2014
ENERGY SERVICE     7085294697       Oct 7, 2014
CUSTOMER CARE     8475928547       Oct 28, 2014
ENERGY SERVICE     8475928798       Dec 4, 2014

These seem like they were probably the same scammers. (224) is local Chicago suburban area code, like 708 and 847. However, no message was left.

POWER DIVISION       2242553379       Dec 5, 2013
POWER DIVISION       2242553379       Dec 11, 2013