just to know where is from or who is this number phone is

to know where is from

I constantly get called from this number, but when I pick up the phone, no one answers me on the other end, and if I call them same thing.  Does anyone know what this mystery number is from.  My husband thinks it's a fax number or something.  All I know is that they call me multiple times a day at all hours of the day and I am tired of it.