ppp config question [math]

[maths <debian_user@21cn.com>]

hello everybody:

chat could not catch the promept "password:"
/var/log/messages show that chat stop at "expect (ssword:)" , then "alarm", "fail", "exit"
my isp's login prompt are "username:" and "password:" 

thank you
            maths
            maths@21cn.com