There is no such thing as "user remains connected into my radius server". It's the client's (here PPPoE Server?) responsibility to act accordingly. In particular it should eventually update the accounting if a "client"/user is MIA. That might be near to the problem you are refering to.
Best regards K .Hoercher- List info/subscribe/unsubscribe? See http://www.freeradius.org/list/users.html
