Dear Sir,
Considering the existing customs valuation rules , the value of the imported goods will done in the following manner in your case :-
1) where the cost of freight/ transport is not ascertainable /(known) such cost will be taken as 20% on the FOB value of the goods.
2) simialry loading /unloading/handling charges will be 1% on the FOB VALUE of the goods
3) and again in the similar circumstances /position the cost of insurance shall be taken as 1.125% of the FOB VALUE of the goods.
it appears that the relevat documents relating to freight element was not presented before the customs assessing authorities at the time of calulation of the customs duty.
thanks,
alok kumar