Called my cell.  I did not answer, and they did not leave a voicemail message.
After researching this phone number on the internet, they are a legit survey company called SQM Group, "a call center industry research organization that conducts customer satisfaction surveys to improve performance for their client companies."

They are exempt from the Fed's Do Not Call List because you have done business with their client, or at least spoken with their client from your phone number (and they are only doing survey work, not selling anything).
Details on that exemption here:  https://www.donotcall.gov/faq/faqbusiness.aspx#who

If they call, either tell them that you want to be removed from their call list (by law, they have to honor that), or call them back at their number and they have a way there to get off their list, or you can go to their website and ask to be removed from their list here:
http://www.sqmgroup.com/do-not-call-list
(they should honor that, and if they don't you can tell the Feds and sue them and their clients)
Normally, it is bad practice to call back scammer calls (they just add you to more bad call lists), but these folks are legit and should honor your request not to call again.
If you know who their client is, you could also call them and ask them never to contact you by phone.

Meanwhile, go to www.endrobocalls.org and sign the petition.  It is by the Consumer Reports Magazine folks, and they are pressuring the Feds and phone companies to give us more control for identifying/managing/blocking calls to our phones.  Spread the word !

I have no idea who or what the person and/or company is.  It is extremely frustrating as they call my cell phone at all hours of the day & night.  I answered ONE time and NEVER answered again.  The time I did answer, there was no one, no response - absolutely nothing & when this comes at 3:00 AM and you have an extremely sick family member, it is quite disconcerting.  I have received about 20 to 25 calls from these %#€£<¥]\#%!  I WANT THEM TO STOP!  It is a very helpless feeling.

Don't care if this is a legitimate survey company or not. However, a legitimate survey company would leave a callback number OR a message. Bothering folks at all hours of the day or night and not leaving messages is, wait for it, unprofessional. Nor is it cool to be demanding folks to go to their website and leaving their contact info to be "removed" from their call list. Duly blocked number.

Some sort of spam

I got rude with them. It was supper time. Tired of all these unwanted phone calls. We pay an expensive phone Bill already so we should have more control.