Had similar experience (only once though, so far that is!)

Same thing happened to me today, April 3, 2008.  Got a call from 303-386-8288, when I picked it up, no answer.  Then they hung up.

They have called my work # every day several times a day and never leaves a message. I finally answered it today and they asked for someone who has worked for our company in 10 years. They then asked for a manager. I told them that I knew they were a marketing call even though they would not identify themselves. Told them to stop calling. We'll see if they stop...

They call constantly. When I pick up - no one says anything.

Constantly get calls from this number.  Usually rings just once and hangs up before I can even answer.

This number calls stating they are representing Qwest and gave give us lower rates.  I told them I didn't believe they were representing Qwest.

Hey "J" you idiot...The calls from this number are coming from a telemarketing company located in downtown Denver, Co. They also have a location in Greely, CO. The name of the former VP of Sales was Dan...but he left years ago AND it is not his business. The web site still shows Dan as the contact...but if you try his extension, it does not work...because he is no longer there. But then again you would know that if you tried calling their main number (720)904-7200 and asked the receptionist.

With this said...stop being an idiot and harassing innocent people. Use your brains not your attitude.

Same telemarketer is calling from 303-386-8283, they've got a bank of OutWATs numbers from ICG Telecom.

Tired of unwanted telephone calls? Google Ogilvy's Worldwide... These hang ups and repeted phone calls are their calling card (no pun intended). Surliness and profanity is the company MO as well as a healthy disreguard for the law and the DO NOT CALL LIST. Get a call? Call the FCC.

Got a call from these telemarketers this morning asking for our I.T. Dept. manager by name but he transferred 2 years ago to a different site. Obviously they're working from an old list of customers they bought from someone. It was a female voice asking if we use Pitney Bowes equipment, but I had to ask the nature of the call before she'd give it up. Fortunately, we have a Procurement Dept. with a voicemail tree so I can xfer them to an "iron maiden" :) The area code and prefix are assigned to ICG Telecom Group, Inc. with the Rate Center and switch located in Denver. That's only relevant to the phone company the telemarketer leases service with, but can be a part of the puzzle.

I can't say enough about how frustrating these people are.  The calls come all the time, including EVERY morning just after 7am, which puts the whole day off to a bad start.  I report and report, both DoNotCallRegistry and here, for what it's worth.  One of the other 303-386-xxxx numbers led me to identifying the outfit.  Googling led me to finding a story about this kid's dad.  I even tried calling the dad at home, but just got a message.  You might want to try that, too.  Calling the numbers back doesn't work (I get a "busy circuit" tone).  Calling the number at the website didn't work for me, either... it goes to a robo-service, but there's no "0" option ("full"), and the extension this kid puts on his website isn't possible to punch in ("if you know your party's extension..." doesn't work, or didn't for me, but try it!).  Here's the outfit, as far as other postings here identify it:
http://tmgmarketing.net
Here's the main little twerp running it:
Contact: Daniel Akre  720-904-7200 ext: 2823
Here's his dad:
Terry Akre
W EXPOSITION DR
LAKEWOOD, CO 80228
303-988-8292
GO GET 'EM!

Missed a call from this number - no message.  Attempted to call back but line just goes blank, never rings.

Recieved last call 9:25 on 1/28/08.  No message & always busy on call back.

Called - left no message

They call and hang up.  When you try to call them back the line is always busy.

I received a call from this number at 9:05 A.M. on 11/2/07.

Receiving calls from this number frequently.

Constantly receive calls from this number. When I do answer, the phone hangs up immediately. Irritating!

These people call, and call, and call, and call.
Tried to call them back, its a bad number
They are never on the other end when you pick up.