I have had 24 calls from this number in the last week...who is this??

THese folks call constantly but never leave a message.

I have had a number of calls.  Some as described already...no answer when picking up the ring.  Just had one though where they claimed to be Bank of America.  After offering no information, they hung up on me?
I even have tried calling back...no answer, line just went dead.  I called and put a fraud alert on my Bank of America cards just in case.
Does anyone know anything about this?
Is there anyone familiar with the Omeha NE area?

This number has called me over ten times.  When  I answer there is nothing for a bit then a dial tone.  I am on the do not call list and have had enough with this number calling me.