# Configuring the NAI for AOC subscription services

If you have subscribed to advice of charge services, to use the services in this manner you must specify which AOC service you have subscribed to when you start the ISDN stack on an NAI
. You can specify this information in the ISDN_PROTOCOL_PARMS_Q931CC structure referenced in the initial call to isdnStartProtocol. The fields to fill are as follows:

- aoc_s_presubscribed

- aoc_d_presubscribed

- aoc_e_presubscribed

For more information, see the Dialogic® NaturalAccess™ ISDN Messaging API Developer's Manual.