Calls frequently, never leaves a message. I am trying to figure out how to block the number from my office phone!!

My dad just donated $25 to them who are these folks?

Does not leave message. This time I answered and they hung up.

Calls constantly on my cell phone and work phone. At least 4 times daily. The number is currently registered through an Ameritech/AT&T landline to the American Purple Heart Service Organization - which is an F rated Charity by Charitywatch.org (formerly AIP). The bot they use just calls constantly and from a couple different numbers.

They keep calling and won't leave a message- shows up on the caller ID as Marshall, Michigan.  I've answered twice and both times there was nobody on the other end- Very annoying.