AsteriskBilling.com - General technical and billing information for VoIP operators using Asterisk PBX.
ANI based prepaid billing is the same as PIN based billing. The only difference is instead of the user entering a pin number to authenticate, their ANI details are collected and stored within the Asterisk billing application and checked by Asterisk when the call is placed.
A good Asterisk billing application will enable different plans to be configured that allow the number of ANI entries to be limited so tiered pricing can be offered based on the number of ANI records the user desires.