Nicor Gas Deny Making Robo Calls, Internet

Nicor Gas, a public utility located in Aurora, Illinois have been making annoying robo calls to me every day or so now for the past coupe of weeks. When I called their office to complain about it I got a customer service representative who said she would check it out. She came back on the line and said, "we are not making any robo calls to your number". when in disbelief I said, "You're not making any robo calls to my number? Then why am I getting them almost every day?" She repeated, "we are not making any robo calls to your number". I found this to be incredible since they are calling me every day. I asked to speak to a supervisor and waited on the line for over a half an hour without anyone coming on the line. Other people have to be getting these annoying calls as well and they have to stop.