I just received a voicemail from 920-494-1812. It was from Martec Grou as mentioned above. They left a voicemail stating they were doing a survey in regards to a phone call I had with Wisconsin Public Service (WPS). I called the number back and she asked me about the customer service I had received when I called WPS. Apparently WPS hires this company to conduct Customer Service Survey's for them.

Please tell me...Yes, I'm talking to you!!!!    Why are you answering these calls?  Why are you calling the number back?  ENOUGH!!  Get Wise!  These people are wasting you time, and you're wasting your time trying to find out who's calling.  Are you that lonely???    If you don't recognize the number you can be sure
it some scammer or the like.   It's amazing, you people think you can get to the bottom of this.  Might as well put these people into the government's category.  You cannot do a dam thing about it.

They called saying they are doing a survey on a/c. I told him to quit calling and take us off their calling list. Guy became an a**, so I banged my phone on the desk! STOP CALLING!! 920-494-1812

They called and left voicemail:

"Hi this is Todd calling from  Martec Research  on behalf of North Shore Gas. You recently had a service call and we're calling to ensure you received good service. Please call us on 888-811-5771."

I received call from this number. found out the toll free number and called back. I answered their survey and I'm sure the answers are not what they wanted to hear. HA HA

No message being left by this caller.

I searched the company name that has been given in other comments and below is the exact number that came up on the caller id when they called here.

Green Bay (TMG Field Research)
1445 North Road
Green Bay, Wisconsin 54313-5725
Map

(920) 494-1812
(888) 811-5755 (toll free)
(920) 494-3598 (fax)

They didn't leave a message they said they would call back. Must not be that important.

I received a call on my personal cell phone from this number on March 3rd, 2010 at around 6pm. They did not leave a voicemail.

Calls many times. Never leaves a message. They call my cell as well. Thats worse because I PAY for those calls.

Called saying it was a customer service survey for UPPCO.

Received a call on my cell which I didn't answer from this number.  They called last week too.  Didn't leave a message either time.

I received numerous annoying calls from "Martec Group Th" displaying the number 920-494-1812.

I received a call from this number. The lady was trying to rich a company named The Right Approach.

I also called back, but on their toll free line. I answered the questions and I'll bet the answers are not what they wanted to hear. HA HA

I called the number back they wan't me to do a survey about tools. I asked them to remove me from ther list.

We also receive phone calls from 920-494-1812.  I plugged the number into GOOGLE SEARCH and came up with:  
The Martec Group
(920) 494-1812
1445 North Rd, Green Bay, WI 54313
http://www.martecgreenbay.com/index1.asp
It sounds like a marketing group or telemarketer].  They NEVER leave a message and if you answer...they wait for you to say "Hello" the second time and then it is a recording because you can't interrupt them with a question etc. So I just hang up.  I don't know HOW they got our phone number because it is UNLISTED!

just got a call from the same number no message left. don't know any one in the michigan area.