NEED HELP!!!! VERY IMPORTANT!!!?

An unfamiliar number called my phone and i didn't answer because i didn't recognize the number. I've tried the reverse phone look up online but all it says is the number is a land line, but won't tell me who it is unless i pay a fee. The number is from around my area, so im thinking it could be something important, so How can i find out who it is by searching the number absolutely FREE?????? Please Help Really Important!!!!