Asterisk A2Billing IVR wrong call duration

Hello,
Will be grateful if someone can help with what seems easy but doesn’t work as expected.
Setup is : A2Billing with Calling Card IVR system - asks for PIN and then dials over outbound SIP channel to a termination provider.
The problem is that the call is billed to customer including IVR duration (not only outbound call duration - as logical).
If end destination do not answer - the call is 0 duration (so IVR duration is not billed in this case).
May be I am missing something basic but…

Regards,

This will be the result of design decisions made by the A2Billing people. This forum does not provide A2Billing support.

You should look into the difference between CDR(duration) & CDR(billsec), and which A2Billing is using.