I have an unlisted number and I don't answer calls I don't know. Calls all the time and leaves no message.

Cancer Support Center looking for donations.
Will continue to try and talk right over you as you tell them to take you off their call list.
I just hung up and added them to my blocked call list on my phone.
I do love my new Panasonic phones with 250 block call spots, but am thinking even that list will fill up quick.

If you try and call the number back, it will just disconnect.

Thanks Rob.  I have received several calls as well.  I tried to do the *60 block and I get a message that the number cannot be blocked.  I may be upgrading my phone if your Panasonic can block.