asterisk users - Sep 2005 - Cannot hear teleco side error message

When we use mobile to call certain number, we can hear the message like, 
" The number you dialed is incorrect", "The customer is currently
is
unavailible" and etc.
But when we use asterisk to call the same number,  just busy tone. We 
found that since version 1.0 it support the standard hangup cause, so we 
base on the HANGUP_CAUSE to fake the error message, but seems different 
teleco's message is different, and sometimes our faked message cause the 
customers confused. So we wonder whether there is  anyway to hear the 
teleco side message directly.