I keep getting one call after another from this number. They won't leave a message and when I call it back the recording says that no one is available to take my call and to call that number back later.

keep getting unwanted calls

I keep getting one call after another from this number. No message.

This number keeps calling and my number is on the national do not call list

Same as everyone else.  Calls, leaves no message.  Cell and home phone.  Probably a bill collector but how would I know?  Not that I'm going to pay them but if I did...?  Kinda lazy on their part.