Who called from 239980452

I called this number back and was hearing funny things

I heard things I dont understand after I called back this number that called me

They called early this morning 24 oct.09 as policy I don't take call from unknown numbers. But was I suprised as to how they got my number. I'm in Nigeria and the international dialing code of the caller is that of Sao Tome and Principle just off my country coast!