Charging Interest on loan in collections
The collection agency is not charging interest....the loan holder is. They report the interest to the CA. Your son will need to call to find out what the interest rate is....will be the same as what you originally signed for. And no, you cannot deal with the hold owner/holder....they have a contract with the CA for them to collect.
Your loan is in default...payments are not report like a current account...the balance may go down (if you are actually paying enough to cover the interest) but payments are not reported posititively.
Really there is not much an attorney can do for you. Private loans will settle but it is up to them for as to how much. Most lenders would rather sue the borrower and cosignor to cover the entire amount.
Why is your son not dealing with this??? It is his loan and credit being destroyed too.