It's a massive NSA operation called Cosmos. A new supercomputing center is now online and they are verifying all operational phones, particularly U.S. cellular phones. A computer-generated call is made to test the hidden functionality within your phone and to activate certain hidden functions. It was supposed to be silent and without displaying an origination number, but many cheaply made processors were built with an architectural flaw necessitating a one time direct call. Only one or two rings are necessary for their computers to connect. It is mostly harmless. Ignore.

Got a call on my cell at 3:30 PM..  Hung up after two rings.  Called back and got an automated message which I could not quite understand.

Got a call from this number and they hung up after only two rings also, as with others who have reported here. What company could this be?

Just got a call from this number on my cell- half a ring then it registered as a missed call-no message left

I got a call from this number at 9:06am March 26, 2010 to my cellphone.  Like many of the others, it rang once or twice and then stopped.

03/26/10 - 3:15 pm  - Called the number back on land line and answered as HEY COSMO - gave options to access my record - but I hung up.

Same as the rest: half a ring and nothing. Mine happened at 7:15 PM.

Possibly a computer dialing random numbers to see which ones are active for telemarketers? Unlike some, I'm not on any of those things like facebook and the like so they didn't get my number that way.

I got it too ..one ring...20:53

Just got a call from this number at 11:50 am on 3/28/2010.  I answered out of curiosity, no one ever spoke they just hung up after a few seconds.

RNK , INC OUT OF MIAMI

Got a call on 3-29-10 @ 5:30 pm.  Didn't leave msg.

I got a call from this number on my cell, didn't even get half a ring and then they hung up.

I got a call from this number at 9:52 am. No message left....who's number is this?????

Got a call at 12:33PM 31MAR10.  Advertisment sponsored by thumbplay.  RINGTONES!!

Call on our birthmom line for adoption...so stressful to recieve scam calls on this line... 1/2 of a ring 11:03 today - then hung up...makes me wonder if it's a potential birthmom who's just frightened...but seeing these notes - I know this is not the case - :(

I just got a call from this number at 4:25 hung up right away. someone is playing games. :(

just got a call from this # 786-837-9810 I am in WASHINGTON STATE 7:09 PM on my cell , no message

I got a call from this number. They didn't leave a message. Don't know who this is either. Weird

I got a call with from this number 4/9. No message. Suspicious as crap.

Received a call from this number 4/8. Didn't leave a message. I'm in Michigan.

I got a call at work and my supervisor was not happy with wasted time.

Received a call from this number today at 11.55am. It rang 2 or 3 times and then stopped. I hadn't intended to answer it anyway, however it was as though they were trying to get me to return a missed call on my phone.

My advice if you "miss" a call from this number, DO NOT return the call to this number, as your returning of calls probably counts as you agreeing/committing to something as I have heard of this type of scam before.

This is the NSA.  Drop the matter already.

Just got a call from this number 786-837-9810 at 6:22 p.m. on 4/6. It rang once and hung up.

Hogwash.  It's so they can sell it to someone else.  It should be illegal.

They hung up after two rings, I don't a soul in Miami, anyone know who this is?

That does not sound harmless, what hidden functions are they activating and how did you gather this info, WHO is NSA? This is making me a bit paranoid. I don't like it

I'm on the do not call list for ever number I have!!!!

I called the number on my land line at work - it answered Hey Cosmo - press 1 for your latest Cosmo blast - I hung up

Just got a call from that number, hung up after two rings