It is a phishing scam pure and simple...The person might not even owe anything but these companies use scare tactics and harassing phone calls like these to make people pay money to make it all go away.
There is a big market in selling uncollected debts. In order to increase the sale price, additional information which does not apply to the original debtor is added. One example is if a debtor with the same name as you ran away, your address and phone number is found in the telephone directory and substituted into the debt information.