i have received calls from this number too and never leave a message.  its like if you call leave a message or something.

I got a call went to voice-mail. but the agent didn't know. She is recorded saying "Hello this call is being recorded, may i Speak with (My first and last name)"
So i think it's a very old collection agent,

These people call every day! I've no idea who they are, but their persistence suggests they're debt collectors.

I've been getting calls every day from this number. Finally blocked them.

These people call daily, finally heard something other than a hang up. Recording telling me, "Hold for the first available representative. It's important that we speak with you." Then some guy finally picks up and asks for somebody who isn't me. Wanted to know if I know this person. Uh, no. He abruptly hung up when I said so. Sounded like a call center in the background.