asterisk users - Jul 2004 - Audiotel - Premium, call proceeding ?

Hi,

here in Italy we have a special kind of phone services that are named
"audiotel", those services are also known as "premium".

Audiotel services are billed in a different way from normal phone
calls and the revenue is shared between the answering company and the
telco, they are used to give weather information, chat party lines and
so on.

Inbound lines are coming over normal isdn PRI interfaces; normally the first 30
second of the call is free and it's used
to make the customer aware of the price.

A telco representative told me that we have to set up an ISDN flag
(call proceeding?) for the first free part of the call and then drop it after
the free message for
billing to start, or the opposite, it was not sure (!).

Anyone of you has ever worked his way with asterisk in a similiar
situation ? Do you know what "flag" we are talking about and how it
can be controlled ?

Tnx !


-- 
Best regards,
 Alessio                          mailto:afoc@interconnessioni.it