I did not answer.  Caller left no message.  Facts about this number, 12 Jan 2013:
Information about number 13123004316:
CNAM: IL CHICAGO,
LRN: 12246556199
State: IL
Ratecenter: BARRINGTON
LATA: 358
OCN: 6115
Company: LEVEL 3 COMM - IL
Prefix_Type: CLEC