get him to check (in C>Dialup Networking)he's using this number to connect: 0808 9933001
if he is and nothing has been changed on his PC (no new software etc)tell him to sit tight cos BT often plays up and will rectify itself.
if he has recently installed a windows update from the microsoft site, that may be causing his probs. my BT connection stopped working after a microsoft update and 1 hour spent on BT's premium rate line didn't discover this!! i had to reinstall windows and set up my BT connection again.
there may be a less drastic cure than that so ask in here if you think microsoft have caused it!
tell him NOT TO PHONE BT UNDER ANY CIRCUMSTANCES he will get free help in here via you and BT probably won't help anyway!
it may just be a temporary local BT problem though so don't worry!