312-940-4340 is being used by COMED (Commonwealth Edison),
for a prerecorded call.  However on my phone display,
it showed a s a call from CHICGOZNO1.

Suspected scam.

Caller ID indicated Chicago IL. Answering grabbed the call but caller hung up. I suspect this is an unwanted call as had a similar call earlier from Chicago with same results. Blocked and off to fantasy land they go.

Got a call, but didn't answer.  Didn't leave a message.

I have been getting recorded calls offering utility services several times per week.  I pressed "1" to speak with an agent to ask to be placed on their do not call list and when I did this, they started acting like they could not hear me and saying unrealted things.  They then started speaking in a foreign language. I repeatedly asked to be placed on their do not call list and they kept ignoring my requests until they just hung up.