Some companies call numbers in consistent intervals all day long to see when you WILL answer your phone; they hang up when someone finally answers and never leave messages on your voicemail. Then they sell that info to telemarketers so they can call when you're more apt to answer.
THIS IS AMAZING! I GOT A CALL FROM A NUMBER THAT IS NOT IN SERVICE!! I HAVE HAD A FEW CALLS BEORE AND IGNORED THEM, BUT THIS TIME I DECIDED TO CALL BACK. GOT THE MESSAGE ' OUT OF SERVICE '. WOW, THAT WAS QUICK!!! HEHEHEHE