Unknown caller (caller id says "NAME NOT FOUND") called. Left no message on answering machine.
When I called it back there is a "Call can not be completed as dialed" recording on it.
SCAMMER! Now it is added to my call blocker.

Display Name not found, no message left. I am running out of space to block calls! UGH!

Unknown caller. Did not leave message. Called immediately after another different scam number.

Did not answer, but I know NO one at this phone number.  I'm 99.9% sure it's a telemarketing call.  

received call from this # (863) 552-3648 and answered....no one answered.  I called the # back later and got a phone company recording saying that the # was not valid.  Later we got a call from Builders Square (210) 301- 0307 and answered and again no one answered on the other end.  We called that back and got a busy signal.  It is on the unwanted calls list too.