I reported them to the DoNotCall registry.  

https://complaints.donotcall.gov/Mobile/Complaint/ComplaintCheck.aspx

They call multiple times a day.

Get 2-4 calls per week from this number. We have caller id on our phones and never answer. Finally, I had it, and answered today. The lady told me she has info reguarding our mortgage, and I started to blast her. She then changed gears a bit, and told me she had info reguarding insurance per our mortgage. I gave her another big time blast, told her not to call here again, especially since we're on the do not call list, and then amazingly, like she didn't hear me, started talking about what she had to offer. I gave her one final blast, unfortunately scaring my dogs, but I doubt she will call here again. I have read your posts in the past because I wanted to know what this number was about, so if it makes anyone feel better, she did get 3 big blasts and if she calls here again the BBB of  WI will be called. I feel better now.

312-878-9520 WILL NOT STOP CALLING. ENOUGH ALREADY.

Call once or twice daily. No message. I finally got fed up and answered and the call disconnected.
No Call List is a JOKE.

How rude!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!.   Get a life.  One that doesn't include harassing people at all hours of the day.

I am getting attempts at least 4-5 times each day.  When I call the number back, it comes up not in service.  I will report to Minnesota Attorney General on line today.

We get this call from 312-878-9520 4+ times a day. ID caller gives name Chicagozn01 and  I found they call from more than 1 number. They hang up after the answering machine voice plays and no message left. This is very annoying esp. when we are getting up in yrs. and not the best of health. I am afraid my spouse will trip and fall someday from rushing to the phone. We are on the DO NOT CALL LIST. What good does it do when these callers don't abide by it. Is this a beacon to them to call us??? Whom ever is in charge of the system for the DO NOT CALL LIST needs to get their act together and do something about this!

They call every day....two to three times per day for the last couple months.  I have never answered.  Has anyone spoke with them and actually found out what they wanted?

This number calls 3 times a day.  This has gone on for the last 3 months.  I am on the DO NOT CALL LIST  What is being done about this?  Anything?????

They have been calling me two times a day for 2 weeks and don't leave messages.  Its driving me nuts.  Next time, I am gonna pick up and scream at them!  Then I will post back and tell you all who the F this is!

Received multiple calls a week fro them.. "GCS" 312-878-9520

Have been getting the same calls several times a day here in Nowhere, Montana for weeks. I too am on the DNC list. This is a bunch of male bovine feces and something needs to be done about it.

Yes.  They called and didn't leave a message.

Anyone else getting calls from this number?

on my called ID GCS an Insurance Co out of PA.

Yes...they've called me twice and didn't leave a message.  The screen was showing "Chicago" and also "GCS"...pretty irritating!

Did you ask for insurance quotes?  That is probably what this is but I already told 1 group that I am not interested anymore and they still call.  I asked for quotes last May or June...come on how long you going to leave it in your system.

They call EVERY DAY, sometimes more than once. Shows up as GCS, as noted previously by others, and no messages are ever left. You'd think they'd eventually get the hint and stop calling since we never pick up.

Finally decided to answer their call after seeing it on Caller ID for weeks (w/o any messages left). After a couple Hello's they asked for my husband who wasn't home and wouldn't answer if he were home. I let them know that he wasn't available and could take a message, the representative said "oh no, no message" then asked what time would be better to reach him, I said never, we'll see if they call back again tomorrow.

I have been getting calls from this number about 2-3 times a week. I don't answer but its getting annoying. They even call in the evening. The do-not-disturb is just a bunch of bologna.

312-878-9520 AND 714-551-9585
They say they are "Insurance Services" They are actually National Union Fire Ins Co Pittsburgh PA. (a member of American International Group (AIG - as in the SOB's we taxpayers bailed out!!!)  
They have already called me 8 times today and have been calling for weeks. I have a phone system that blocks calls but their dialer doesn't get the hint. I called them to tell them I'm on the DNC list but only got a "take me off your list mssg.

Their Address is listed as:
175 Water Street, 18th Floor
New York, NY 10038
Phone: 212-770-7000
Web: www.chartisinsurance.com

Called last night and this morning. Yes, we are on the do no call list. If these calls were legitimate I would assume they would leave a message.

If you didn't use all CAPS, I might stop to read what you wrote.

I just got a call from this number, which showed up as "GCS" as some others have noted. I didn't answer, and there was no message. I'm on the "do not call list" but I'm beginning to think that the exceptions have swallowed the rule!

Called, four or five times each at a different time of day

THIS IS ABOUT THE THIRD OR FOURTH TIME WE RECEIVED A PHONE CALL FROM THESE PEOPLE, HOWEVER THESE PEOPLE NEVER LEAVE A MESSAGE. WE ARE SICK AND TIRED OF ALL THESE SCAM CALLS. YES, I SAID, "SCAM CALLS, BECAUSE THAT IS WHAT THEY ARE." WE ARE SICK AND TIRED OF THE REPS FROM NO-CALL LISTS SAYING TO US THAT YOUR NUMBER WILL BE PUT ON THE NO-CALL LIST AND THAT NOONE WILL NOT CALL YOU, YEAH RIGHT..... THEY ARE JUST LIEING TO EVERYONE WHO REGISTERS THE PHONE NUMBERS TO WHICH THEY DO NOT WANT TO BE CONTACTED. MY PHONE READS: GCS AND THEN THE NUMBER. STOP THE SCAM CALLING, STOP THE SCAM CALLING, STOP THESE PEOPLE FROM CALLING EVERYONE, STOP THESE PEOPLE FROM CALLING EVERYONE!!!!!!!!! HEY CONGRESS, THE PHONE COMPANY, SOMEONE..... WAKE UP!!

What good is no call list?  I get more calls from telemarketers now, than I did before I registered with "no call list".   I think the reps at "no call"  are selling info to telemarketers!

Get at least 4-5 calls from them each week. I don't answer, they don't leave message.

Called my number (on Do Not Call Registry for years) 3/9, 3/10, 3/11.  I don't answer; they leave no message.  Caller ID says "GCS" - probably just another annoying telemarketer who doesn't respect the law

This number called today and it just came up as Chicago, IL on my caller ID.  I called it back, and it just said Insurance Services; however, it gave you the option to remove your phone number off their marketing list.  When I did that, it said they are National Union Fire Insurance Company of Pittsburgh PA.  It said it will take up to 30 days to remove my information.  I'm mad, because I am on the National No-Call list.  I'm filing a complaint against this company for calling me.