DHL Express India — dhl express asking additional amount saying duty

Address:

Ernakulam, Kerala, 682030

My friend ordered a parcel as a gift for me from hong kong to bangalore via express service. It came in a day to bangalore and later it delayed for customs checking. I then followed with customer care to get their customs in charge who asked to provide details of po and bank statement as customs hold for low declaration. I provided immediately but then no response. After follow up i was told i sent a po with, 206 newzealand dollars but the seller has declared $50. As my friend had booked online i don't know what the seller declared, however, provided details as possible. Later they asked me to provide a clarification letter for the difference which i sent. Again no response from them.
Then they submitted to get released but after all these messes, they charged 7303 rs as duty fee. Some person from the customer care after my constant bickering had sent me an express cargo clearance invoice (Which doesn't even look reliable) which states an amount of 6123.61 inr. Then they are adding up another 1000+ inr for collecting it from customs they said. So now, i am supposed to collect a gift worth 9000 inr (Converting 206 nzd to inr) giving 7303 inr which is almost the actual amount of the commodity.in addition, the sender (My friend) has given almost 20 nzd as transportation charges for dhl.