Who called from 2402048750

Received a call, from this number, on 5/18/15, for the first time.  Came in on the landline at 11:19AM, EDT.  CID is Silver Sprin MD.  Don't know anyone with that number; didn't answer, no voicemail left.  No clue!

I didn't recognize the number, so didn't pick up.  But it was a follow-up call from a seminar I attended a couple of nights ago.

They Called and I answered and they hung up. I called back and the recording says that its The National Marketing Company. To remove future calls from your phone it says to hit zero. I did and the call ended.

A call came in from this number and I did not answer.  They did not leave a message.