keeps calling does not leave a message.

This number has called 4 times in the last 5 days - twice today just one hour apart. I don't answer it, but recorded dates and times and have now added it to Call Rejection on my phone.VERY ANNOYING! It interrupted an important call I was on, which I had to end prematurely, only to find out it was this same spam number who had come in on Call Waiting. That was the last straw!

Calls numerous times throughout the day. Very annoying

I called the phone number and received music on hold then a recorded message that said to call back during regular business hours.  The message then proceeded to say if you want more information, press 1, if you want to be placed on the do not call list, press 2.  I pressed to and the message stated after 72hrs my phone number will be placed on the do not call list.

I called back and requested to be put on do not call list. They indicate that they call on behalf of 'organizations' and mentioned campaigns.
I personally think it may be Fire Chiefs association. They call twice yearly and never leave message.