cisco 801 problem

i'll need some help on this .
i've got a router on a lan > hub > router>isdn line>isp

when a user needs an internet connection the router open channel A , if needed it also opens channel B. The problem is that even if i disconnect the router from the hub channel A doesn't close. The router keeps it open for some reason. Now i made it work last year so if anyone can help cause i don't remember anything.

the listing can be send via mail if you want
any opinions are greatly apriciated.

stergios