To everyone looking up this number, it's a "zombie debt collector". They aren't the people who have your original debt, it's been sold on to a secondary collector. This may be a debt that's old, and since the first or second collection agency didn't get your money, your debt was sold to these zombies. Google zombie debt collector and you'll find more. It depends on your state, how long they can harass you over it, but if you can prove it's too long ago for them to call, you can get your state's attorney general to get it to stop. Good luck out there, and keep on checking the numbers!