THAY CALL ALL DAY LONG WHEN I ANSWER THERES NO ONE THERE

Received a phone call from this number on 2/5/2014 at 7 PM, left no message.  Called back to see who it was and the number has been disconnected.  SCAM

Whoever is calling they are calling everyday around the same time but the last two numbers are changed, so they are calling from different numbers.

I would like to know who is calling from this number? They call all hours of the day....