A scavenger bill collector.  Convergent is their name.  They call but don't leave a message.  They try to collect on old debts they buy from other collection agencies who couldn't collect, so they really are at the bottom of the barrel.

Answered one call; told them that no one with name they were asking about was associated with business telephone number being called.  Have received two more calls.  Answered call; no one on other end of line.

I received a call from this number. No one said a word. No machine or anything.

Hung up when I answered.