Asterisk A2Billing customization

Hello, I already have the latest a2billing version installed and working properly. How a2billing works normally is when a call is made the call shows as connected, even though the call is still ringing. The a2billing script does charge it correctly, even though the user calling from a softphone or linksys show as already connected since it started to ring even though the call hasnt been answered yet. We have some external call charging hardware that connect to linksys pap2, but they are charging the calls when it gives connected signal (when it starts to ring). So it is charging calls even when they are still ringing (also called False Answer Supervision FAS), instead of when the call is actually answered. What we need is to have a2billing to not give an Answered signal when it rings, only when the call is actually answered. We already changed the basic system configuration inside the web a2billing page, from Manage Call to No/Yes, etc. Those changes don't do what we need. We most likely need some custom coding in it. Thanks, Wally