It's because they are bill collectors. If you owe a company they pay these guys to harass you till you pay your bill. That's why they keep calling, trying to get you to settle and pay off what you owe.
Well, they may or may not be legit but they called me and I don't have any bad debts whatsoever. I don't owe anybody Jack crap and I don't have anything I have defaulted on yet they called anyway so as far as I am concerned they are a scam