oh, sorry for the misleading words..
yeh i was referring to the "telephone cable" from the base to the telephone socket. The telephone cable I tested works with normal phones, but not B&O ones... Dealer told me to get a B&O cable...
By the way... i found that particular store in HK was so unprofessional... they did not stock any of those cables... and asked me to buy the one they've been using (no idea for how long)... and of course, I walked off straightaway...