Periodicals Obvious scam? Hamilton, Montana

My son received a cell phone call recently telling him that he owed $700 to a company. They said that it was for magazines. He does not receive any magazines in the mail so he was really confused and more than a little concerned. 
Then a few days later an ESPN magazine arrived with his name on it. He did not order it, so he called the number on the magazine to let them know he did not order it and they said they had no record of an order in their system but to call another number they gave us. When we called that number the person on the other end of the line said that the order was placed through something called Countrywide. They said they would notify them that my son did not order or want the magazine. 

 It has been a month since that phone call and there was no further contact until today when he received a letter. At the top of the page is "Periodicals, PO Box 1950, Hamilton, MT 59840, 1-888-300-9415"
The letter says, "Past Due Notice- Your account is seriously delinquent and an audit of our records has sorted your account out for special follow-up. In order to stop further action, on our part, your payment much reach us in 5 days." It also says " To avoid finance charges please remit the amount due by 9/23/11". (Today is 9/12/11) At the bottom of the page it says:
Current charges      Past Due Amt     finance charge    total amt due     due date
33.20                      66.40                 0.00                    99.60               9/23/11

The name and address of the company is then printed again at the bottom. 

Several things jumped out at me about this letter. The most important thing is that it does not say what the money is owed for. No where does it mention "magazine subscription" or anything else. 
My son is developmentally disabled and does not have a credit card. He does have a cell phone so I fear that this has all come about from a hacking of name, address and cell number from our cell phone company. 
Not sure what to do now. I know that we will not be sending any money as it is obvious that this is not a legitimate company nor do we own them any money. Any thoughts?