The guy left a weird message. He repeats the call back number then leaves the message below:
"As this involves an unusual case downloaded against your name and a couple of serious allegations, is going to be pressed against your social identity. And if you fail to return this call, the next notification will be given to your current employer, references, and family members. So before you end up losing your job and your references, and your family members get legally contacted, get back to me on my number, and ask for me, Kenneth Johnson. Goodbye."
He starts of speaking sternly, but by the time he gets to, "So before you end up losing your job," he is full on yelling into the phone.
Since his English is incorrect, and he speaks in a thick accent, I would wager he is a scammer, impersonating a debt collector.