I have no idea who these people could be, but when i answered the phone i was directed to a automatic voice thing, it also stated that they were a debt collector. So be aware of this number and just keep hanging up on there [***]. They will get the message soon enough, the only thing that bothered me is they called at 9:00 at night.
Don't just hang up on them. Doesn't get rid of them. Instead use the internet to find their address, ask for written proof of the debt and inform them that their message about being a debt collector is a violoation of the law.