This number has called my cell phone multiple times per day, sometimes in the middle of the night but has NEVER left a message.  I never answer numbers I don't know, but my husband also got calls from this number and accidentally answered it because he was waiting for a call that he knew would be out of state. He said the person who answered asked for him by name, and had a thick accent (he described it as possibly Indian or Middle Eastern). My husband verified that he was the person the caller asked for, and the caller then asked to speak with his wife. At that point in time, he knew it wasn't the call he was waiting for. My husband said "may I ask who's calling please?" And the caller got very agitated and refused to answer his question. My husband then said "if you're calling me to ask to speak with my wife, I'm not allowing you to speak with her until you tell me who you are and why you're calling", and the caller replied by cussing him out and telling him to go f&@k himself, so my husband hung up.
Later that day, my mother-in-law called me to warn me of "solar panel scammers" who have been calling her, and one of the four numbers she gave me was the same number my husband answered and got cussed out by. She told me when she answers these solar panel scam calls, if she tells them she's not interested or that she already has solar panels, the person she's speaking to (she said it's always a thick, heavy accent; possibly Indian or Middle Eastern) will cuss her out and/or make very sexually explicit remarks toward her.
Please be aware of these callers. My best advice for everyone is DON'T ANSWER A CALL IF YOU DON'T KNOW THE NUMBER! And if it really was an important call, THEY'll LEAVE A MESSAGE! :)

For a cell phone, some already have call blocking, if not, there are free apps on the web that will work for some. You can google this. If you have a smart phone, there is a free app called call control. Iphones appear to have apps also. Another one is called Mr. Number. For tracfone & straight talk:

https://play.google.com/store/apps/details?id ... .tracfone&hl=en
http://extras.straighttalk.com/en
http://www.youmail.com/home/carriers/straight-talk/block-number
https://www.straighttalkwirelessforum.com/viewtopic.php?f=6803&t=55006

For text messages: forwarding any text message spam you get to the short code  “7726,” which spells “spam” on most phones, to alert your network operator to the abuse. ATT won't accept 7726 But they will accept BLOCK and return a message that the web site is blocked. forward the texts to 7726 or BLOCK, depending on your phone carrier.
http://www.att.com/esupport/article.jsp?sid=KB115812

Report your callers here, not just to the DNC alone:

https://www.ftccomplaintassistant.gov/#&panel1-1
https://consumercomplaints.fcc.gov/hc/en-us
https://complaints.donotcall.gov/complaint/complaintcheck.aspx?panel=2

By State DNC lists:
http://800notes.com/res/DoNotCall.aspx

http://800notes.com/forum/ta-d20d86fdc3e145c/reporting-international-scams
https://www.econsumer.gov/#crnt

To file complaints on Foreign company's:
eConsumer.gov: Report Your Complaint
E-mail: econsumerwb@ftc.gov

Thank you for this information, I too get calls with no known name or caller ID.  So, just like you, I don't answer #'s I don't know or recognize and if it's important or someone that you called and left a message with; then they will leave one as well.

Unknown phone number that didn't leave a message. We have blocked number!!