These dicks call you, and you call them back; it's a loophole telemarketers use to scam people by claiming "you called/were referred to us, we're not harassing you". Law enforcement won't/can't do anything about it, and they constantly use different numbers, so it's impossible to stop, essentially.
I get calls from this number (402-206-0161) several times per day. I don;t know what good it does them, because when I answer, there is nothing but silence. No sales pitch, no threat for collection, no survey, NOTHING!. If I call the number back, there is nothing but a recording telling me to press 1 if I wish to no longer receive special offers from this number. Strange, since there never WAS a special offer. Never a person either. It's just harassment, or someone is trying to find out which times of day I answer the phone.