Detention and Show Cause Notice From Customs Department

Hi, I recently received a Detention and Show cause Notice from custom office (i.e foreign Post Office) and was asked to furnishing the following documents 1) Purchase Invoice/Commerical Invoice 2) Transaction Details/Payment Details 4) Copy of any one document(Pan Card/Driving License/Aadhar Card/Voter ID) Also to asked whether I want to be heard in person before adjudication or otherwise. The item is a phone which costs more than INR 50,000/-, however, It is a gift (if you can believe) the invoice is in the name of a relative (NRI) who purchased it from US and have send it to me - which I can get it from him to forward further. But, I have not paid for this and he had sent as gift - a token of love and affection. How do I reply to the custom Department and how can I take them in confidence that its a gift and I have not paid a penny for the phone. I can show them the bank transactions etc. but not sure if I should send it or not without any demand from the custom department. Please help. Its been 2 weeks now that the Item is stuck in the foreign post office