Hi Prateek,
The major difference between Billback and Chargeback can be understood by the reading the process for both Vistex IP in the links below.
Chargebacks
https://help.vistex.com/legacy/help/60A/IP/Vistex_-_IP_Chargebacks_Documentation/whnjs.htm
Billbacks
https://help.vistex.com/legacy/help/40C/IP/Vistex_-_IP_Billbacks_Documentation/whnjs.htm
