Howto
From x164 documentation wiki
Set up DIDs
Set up customer profiles with prefix dialing]
Establishing usage quotas for users]
How do I limit the usage of a subscriber per month?
In the 'Quota usage' table there is an entry for each customer and carrier included in the database. Update the 'Quota' field of a record to set a limit for a subscriber. When the count in the 'This Month' field exceeds the quota, the subscriber (customer or carrier) is blocked. When a subscriber is blocked his corresponding entry in the 'Customers' or 'Carriers' table has the field 'Blocked' set to '1'. To unblock a subscriber simply update this field with a '0'.