been getting calls all week from this number:  720-452-5525.  Leaves no messages, just keeps calling.
The caller ID says "Contact Center"

I work in a school system and when I continuously get calls from numbers such as: 720-452-5525, 701-557-9150, and so on;  when you ask them where they're calling from and they can't speak proper English, their connection is horrible and they lie.  The best one begins with:  "The FBI ........, etc. (who have several numbers).  I can't count the number of times I get calls from THAT one each day.  ALL OF THEM should know where they're calling and who they need to ask for.  They need to stop bothering people with their simple sales pitches while trying to intimidate with government names, etc.

This number has been calling my phone for days now....720-452-5525.  Until today, I never answer.  When I did, the phone on the other end hung up.  I don't know who they are but worry that there is a scam out there if you pick up the call they can access information or something...I thought I heard about it on the news a couple of weeks ago that if you answer...oh shoot. I can't remember but I know I should NOT have answered!  I would advise anyone else to not answer even though it's very tempting.

I got this call and was told it was modern salon (I'm a hairdresser) they wanted to renew my subscription.

Listed on caller id as 'Call Center'. No answer.

Answered call and caller immediately hung up.  Caller ID displayed Contact Center from Denver CO.  Blocked number.  Agree with ladygeek that this was an automated call and add that it is also harassment.  Have always told telemarketers to put me on their do not call lists and don't ever contact me again.  Don't know if that is related here.  Have had a number of these types of calls lately.  Too bad, the feds don't care about policing these criminals.  They should.  People have a right to be free from harassment.

Another magazine telemarketing call from Ebsco Magazines  "Electronic Design" magazine

Just got a call from this number on my cell phone

got a call on my work phone from 720-452-5525.  'they' left no vm.  caller id says "CONTACT CENTER" in all-caps.

got a call from 720 452 5525 on 28th march evening. and i answered, they hung-up on me.

Called cell.  No message.  No Caller ID.  SPAM

I just received a call from this number.  I didn't pick and let it go to VM.  It must be an auomated call because when I block a number, my app, leaves dead air on my VM.  Automated systems generally only react to real voice.  That's my opinion on the matter and everyone has one so I'm just going to block the number.

"Contact Center" on caller ID, hung up the second I picked up.

Received call from this number.  When I picked up, said hello, there was a click and then a busy signal.  Comes up contact center on caller id.