Indian Customs — charging enormous duty amount

Address:

Hyderabad, Andhra Pradesh, 500081

I have ordered a shipment of laptop bag worth approximately inr 8500 from australia through fedex. When i received it, they have asked me to pay 9500/- as part of duty. When i enquired about the same the fedex agent told that the customs officer has appraised this bag to be worth 21000/- and thus asking me to pay duty and gst based on his appraisal. I have an invoice and also credit card statement that says i have bought this item for inr 8500/-.

What can i do in this case to get this situation fixed?